Data from the NATIONAL VITAL STATISTICS SYSTEM Characteristics of Births United States, 1973-1975 A presentation of characteristics of live births, including educa- tional attainment of parents, birth weight, period of gestation, pre- natal care, sex ratio, month of birth, attendant at birth and place of delivery, plurality, illegitimacy, and interval since last live birth and last pregnancy, and outcome of last pregnancy. Emphasis is on births occurring in 1973; however, data for 1974 and 1975 are in- cluded in the summary and in the discussion of trends. DHEW Publication No. (PHS) 78-1908 Series 21 Number 30 U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE Public Health Service National Center for Health Statistics ‘ Hyattsville, Md. September 1978
Transcript
Data from theNATIONAL VITAL STATISTICS SYSTEM
Characteristics of BirthsUnited States, 1973-1975
A presentation of characteristics of live births, including educa-tional attainment of parents, birth weight, period of gestation, pre-natal care, sex ratio, month of birth, attendant at birth and place ofdelivery, plurality, illegitimacy, and interval since last live birth andlast pregnancy, and outcome of last pregnancy. Emphasis is onbirths occurring in 1973; however, data for 1974 and 1975 are in-cluded in the summary and in the discussion of trends.
DHEW Publication No. (PHS) 78-1908
Series 21Number 30
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFAREPublic Health Service
National Center for Health Statistics‘ Hyattsville, Md. September 1978
Library of Congrass Cataloging in Publication Data
Querec, LindaJ.
Characteristics of births.
(Vital and health statistics: Series 21, Data from the National Vital Statistics System;no. 30) (DHEW publication no. (PHS) 78-1908)
Bibliography: p. 271. Childbirth–United States–Statistics. 2. Prenatal care–United States–Statistics.
I. Spratley, EmelI, joint author. II. Title. 111. Series: United States. National Center forHealth Statistics. Vital and health statistics: Series 21, Data from the National Vital Statis-tics system, Data on natalit y, marriage, and divorce; no. 30. IV. Series: United States. Dept.of Health, Education, and Welfare. DHEW publication no. (PHS) 78-1908. [DNLM: 1. Vitalstatistics–United States. W2 A N148vu no. 30]HA211.A3 no. 30 [HB915] 312’.1’73s [312’.1’73]
ISBN 0-8406 -0135-2 78-15448
—For sale by the Superintendent of Documents, U.S. Government Printing Offke
Washington, D. C. 20402
Stock No. 017-022A2C64C-5
NATIONAL CENTER FOR HEALTH STATISTICS
DOROTHY P. RICE, Director
ROBERT A. ISRAEL, Deputy Director
JACOB J. FELDMAN, Ph.D., Associate Director for AYzalysis
GAIL F. FISHER, Ph. D., Associate Director for the Cooperative Health Statistics System
ELIJAH L. WHITE, Associate Director for Data Systems
JAMES T. BAIRD, JR,, Ph.D., Assockzte Director for International Statistics
ROBERT C. HUBER, Associate Director for ManagementMONROE G. SIRKEN, Ph. D., Associate Director for Mathematical Statistics
PETER L. HURLEY, Associate Director for Operations
JAMES M. ROBEY, Ph. D., Associate Director for Program Development
PAUL E. LEAVERTON, Ph. D., Associate Director for Research
.4LICE HAYWOOD, Information Officer
DIVISION OF VITAL STATISTICS
JOHN E. PATTERSON, Director
ALICE M. HETZEL, Deputy Director
ROBERT L. HEUSER, M. A., Chiej Natality Statistics Branch
RITA U. HOFFMAN, Chiej Programming Branch
MABEL G. SMITH, Acting Chiej Statistical Resources Branch
Vital and Health Statistics-Series 21-No. 30
DHEW Publication No. (PHS) 78-1908Library of Congress Catalog Card Number 78-15448
Summary of PrincipaI Findkgs .................................................................................... .........................
Education .... ......................................................................... .................................................................Education of Mother ........................................................................................................................Education of Father ... ......................................................................................................................
Birth Weight ..........................................................................................................................................Education of Mother ....................................................................... .................................................
Period of Gestation ............................................. ......................... ........................ .................................Education of Mother ........................................................................................................................
Month of Pregnancy Prenatal Care Began .. ............................................................................................Percent Low Birth Weight ......................................................................................... .......................Education of Mother ........................................................................................................................
Number of Prenatal Vkits ................................................................... ..................................................Percent Low Birth Weight .................................. ..................... ................................................... ......Education of Mother ................................................................... ............... ......................................
Sex Ratio of Births ......... ................................. ......................................................................................
Month of Birth ......................................................................................................................................
Attendant at Birth and Place of Delivery ...............................................................................................
Interval Since Last Live Birth ................................................................................................................Education of Mother .................................................................. ......................................................
Interval Since Termination of Last Pregnancy and Outcome of Last Pregnancy ....................................Percent Low Birth Weight ................................................................................................................
Illegitimacy ................................. ..........................................................................................................Education of Mother ........................................................................................................................Percent Low Birth Weight ................................................................................................................Prenatal Care ....................................................................................................................................
1. Percent of Eve births prematwe, byageof motiermd mce:totd of40repotiing States mdtieDistrict of Columbi~ 1973 ............. .............................................................................................
2. Median birth weight bypenod ofgestation adrace: totdof40 repofiing States mdtie Districtof Cohunbia, 1973 .......................................................................................................................
1
1
223
35
57
789
101011
11
13
14
16
1719
1920
20242425
27
28
46
6
7
...Ill
3. Percent of births tomothers beginning prenat.al care during the first Zmonths ofpregnancy, byageofmotherand race and Iive-birth order and race: total of 42 reporting States and the Di<trictof Columbia, 1973 .......................................................................................................................
4. Sexratio bymonth of birth andrace: United States, 4-year average, l97O-73 ...............................
5. Monthly indexes oflivebirths, byrace: United States andeachre@on, l973 ................................
6. Percent of Iivebirths occuming inhospitds, bycolor: United States, 1960-75 ...............................
7. Mean interval since last live birth, by age of mother and live-birth order: total of 40 reportingStates andthe District of Columbia, 1973 ............................................... ....................................
8. Estimated ille@timacy rates, bya~ofmother andcoIor: United States, l94O-75 .........................
LIST OF TEXT TABLES
A. Perceot of live births of 2,500 grams or less by age of mother and live-birth orde~ United States,1973 ............ ................................................................................................................................
B. Percent distribution of live births by period of gestation and race: total of 40 reporting Statesand the District of Columbia, 1973 ............ .................................................................................
C. Percent of live births premature by race and educational attainment of mother: total of 37 re-porting States and the District of Columbia, 1973 .......................................................................
D. Percent of live births of 2,500 grams or less for each month of pregnancy prenatal care began,by race: total of 42 reporting States and the District of Columbia, 1973 ....................................
E. Median number of prenatal visits by month of pregnancy prenatal care began and race: total of37 reporting States and the District of Cohsmbia, 1973 ...............................................................
F. Percent of live births of 2,500 grams or less by number of prenataf visits and race: total of 38reporting States and the District of Columbia, 1973 ....................................................................
G. Median number of prenataI visits by educational attainment of mother and race: totaf of 37 re-porting States and the District of Columbia .................................................................................
H. Sex ratio by race: United States, 4-year average, 1970-73 ..............................................................
J. Sex ratio at birth by race and plurality: United States, 1971-75 ....................................................
K. Sex ratio at birth by live-birth order and age of mother: United States, 1973 ................................
L. Monthly indexes of live births and standard deviations: United States, 1960, 1970, 1973, and1975 ........................................................................................... .................................................
M. Ratio of plural live births to total live births by age of mother and race: United States, 1973 .......
N. Median birth weight and percent of live births of 2,500 grams or less, by plurality and race:United States, 1973 .............................................. .......................................................................
O. Mean interval since last live birth by live-birth order, age of mother, and race: totaf of 40 re-porting States and the District of Cohrmbia, 1973 ............ ...........................................................
P. Mean interval since termination of last pregnancy by outcome of last pregnancy, live-birthorder, and age of mother: total of 39 reporting States and the Dktrict of Columbia, 1973 .........
Q. Estimated illegitimacy rates by age of mother and race: United States, 1970-75 ............................
R. Estimated illegitimacy ratios by age of mother and race: United States, 1973 ...............................
S. Percent of live births illegitimate by educational attainment of mother and race: totrd of 33reporting States and the District of Columbia, 1973 ....................................................................
8
13
14
15
18
22
4
6
7
9
10
11
11
12
12
13
16
16
17
20
23
24
24
iv
T. Percent of live births of 2,500 grams or less by legitimacy status, age of mother, and race: totrdof 38 reporting States and the District of Columbia, 1973 .. .. .. .. .. ... .. . .... .. . ... .. .. ... .. . .... . . .... . .. .... . .. .. 25
U. Percent of live bkths of 2,500 grams or less by educational attainment of mother, legitimacystatus, and race: total of 33 reporting States and the District of Columbia, 1973 . . . .... .. . ... .. .. ... .. . . 25
V. Percent distribution of live births by month of pregnancy prenatal care began, by legitimacystatus, and race: totrd of 33 reporting States and the District of Columbia, 1973 .. . .. .... .. .... .. . ... .. . 26
SYMBOIX$
Data not available -------------------------------------- -..
category not applicable ----------------------------- . . .
Quantity zero ------------------------------------------ -
Quantity more than Obut less than 0.05---- 0.()
Figure does not meet standards ofreliability or precision -------------------------- *
I 1
CHARACTERISTICS OF BIRTHS
Linda Querec, M. A., and Emell Spratley, Division of Vital Statistics
INTRODUCTION
This report describes important character-istics of births occurring in the United States.Much of the analysis was completed before 1974and 1975 data became available. Therefore, datafor 1974 and 1975 are included in the next sec-tion, “Summary of PrincipaI Findings,” andthroughout the remainder of the report when-ever trends are discussed. The major data in thisreport, however, concern the characteristics ofbirths occurring in 1973.
Birth statistics presented in this report arebased on information obtained from the certif-icates of live birth filed throughout the UnitedStates. Data for a number of the charactenstics–educational attainment of parents, interval sincelast live birth, interval since termination of lastpregnancy, outcome of last pregnancy, legiti-macy status, month of pregnancy prenatal carebegan, number of prenatal visits, and period ofgestation–are based on items that are not re-ported on the birth certificates of all States.Because data on these characteristics are basedonly on information for residents of reportingStates, caution should be used in extrapolatingthese statistics for the United States as a whole.aMoreover, there may be variations in a particularstatistic from one table to the next, dependingon the number of States in the reporting area forwhich the statistic is computed. For example,the incidence of low birth weight (2,500 grams
aAlthough legitimacy status was not reported on thebirth certificates for all States, national estimates of il-legitimate births have been prepared on the basis of datafor the reporting States.
or less) was 7.6 percent for the entire UnitedStates in 1973. The incidence was 7.3 percentfor the 41 areas which reported informationfrom which the interval since the last live birthwas derived, and 7.5 percent for the 43 areaswhich reported month of pregnancy prenatalcare began. Table I in the appendix shows thereporting areas for each of the characteristicsnot reported by all States.
SUMMARY OF PRINCIPAL FINDINGS
In areas reporting education, the majority ofbirths occurred to mothers who had at least ahigh school education. In 1973, these were 69.4percent of all births; by 1975 this proportion in-creased to 71.4 percent. Infants born to motherswith less than 12 years of schooling were morelikely to be of low birth weight (2,500 grams orless) and to be premature (less than 37 weeks ofgestation) than were infants born to motherswith more education. Moreover, these less edu-cated mothers were less likely to receive pre-natal care early in pregnancy and were morelikely to have an illegitimate birth than theirbetter educated counterparts.
The median birth weight for a.11 infantsborn in 1975 was 3,320 grams, or 7 pounds, 5ounces. Seven percent of all newborns were oflow birth weight–that is, they weighed 2,500grams (5 pounds, 8 ounces) or less. The medianbirth weight of black infants was somewhatlower than that of white infants, reflecting aconsiderably higher incidence of low birthweight among black infants than among whiteinfants-1 3.1 percent compared with 6.3 percent
1
in 1975. Failure by some investigators to elimin-ate the large racial differential after accountingfor differences in maternal ~haracteristics andother factors known to be associated with lowbirth weight suggests that genetic as well as en-vironmental factors may be affecting the ob-served differences.
Premature births (born before 37 weeks ofgestation) comprised 9.2 percent of all livebirths in reporting areas in 1973. There was alarge raciaI differential: 16.7 percent of blackbabies compared with 7.7 percent of whitebabies were classified as premature. In 1975, 8.9percent of all live births were premature, andmost of the decline was among black infants.
In 1973, among States that reported themonth of pregnancy prenatal care began, nearly71 percent of all births were to mothers whostarted care during the first 3 months of preg-nancy and only 1.5 percent of all births were tomothers who received no care; there was littlechange in these figures between 1973 and 1975.For all mothers who received care and residedin areas reporting this item, the median numberof prenatal visits per birth was 10.6. The com-parable numbers for white and black births were10.9 and 8.6 visits, respectively. By 1975, themedian number of prenatal visits had increasedto 10.8, and there was a larger increase for blackthan for white births.
The sex ratio at birth varies little from yearto year; it was 1,054 mzde births per 1,000 fe-male births in 1975.
Almost all (99 percent) infants born in theUnited States during 1975 were classified aahaving been delivered by physicians in hospitals.The gap between the proportion of white birthsand black births occurring in hospitals continuedto narrow in 1975 —98.9 percent of white babiescompared with 98.0 percent of black babies.
In 1973, of 57,721 live births that occurredin plural deliveries, the overwhelming majoritywere twin deliveries. The multiple birth ratiowas 18.4 live births in multiple deliveries per1,000 totaI live births. The ratio was 22.2 forblack births compared with 17.7 for whitebirths. In 1975 these ratios were slightly higher(19.2 for all live births).
For all second and higher order births toresidents of States reporting the date of last
live birth, the mean interval since the last livebirth was 43.3 months in 1973. The mean in-terval since termination of the last pregnancy forall births resulting from second and higher orderpregnancies was 40.4 months. This interval wasapproximately l?12 years longer when the lastpregnancy ended in a Iive birth than when itended in a fetal death. By 1975, the intervalsince last live birth had increased to 44.6 monthsand the interval since termination of last preg-nancy had increased to 41.4 months.
The estimated illegitimacy rate was 24.8illegitimate births per 1,000 unmarcied womenaged 15-44 years in 1975, a decline from therate of 26.4 in 1970. In spite of the decline inthe rate, the illegitimacy ratio had increasedfrom 106.9 to 142.5 illegitimate births per1,000 total live births between 1970 and 1975,a result of both the decrease in marital fertilityand the increase in the number of unmarriedwomen.
EDUCATION
The educational attainment of both parentswas first tabulated in 1969. It is defined as thenumber of years of school completed in publicor accredited private or parochial schools and isuseful as a measure of socioeconomic status. The1973 data presented in this report were obtainedfrom 41 States and the District of Columbia.
Education of Mother
The proportion of births whose motherscompleted 12 or more years of schooI by age ofmother, live-birth order, and race is shown intable 1. Mothers aged 15-19 years were morelikely to have less than 12 years of educationsince most 15- and 16-year-olds have not yetcompleted high schooL Of all births to mothersin this age group, 19 percent were to 15- and 16-year-old mothers who would very likely not yethave had the opportunity to complete highschool. The proportion of births to motherscompleting high school rose with age to a peakof 82.8 percent for the 25-29-year age group andthen declined to 58.9 percent for the oldest agegroup. Similar age patterns were found forboth race groups. The percent of births to
2
nothers completing at least 12 years of schoolvas higher among white births than among black>irths for each age-of-mother group. The racialiifferentia.1 was not as great among younger~omen as among older women. For the 20-24-,’ear age group, the proportion of births tonothers who had completed 12 or more years~f school was 19 percent higher among whitesthan among blacks. This differential increasedwith age to 77 percent for women aged 40 yearsand over.
For each age-of-mother group the propor-tion of births to mothers with 12 or more yearsof school tended to be inversely related to birthorder. For all ages combined, however, this pro-portion increased from 70.7 percent among firstbirths to 76.1 percent among second births, aresult of the fact that the distribution of birthsby age is not the same for all birth-order groups.For example, more than a third of first birthsare to mothers aged 15-19 years, but only atenth of second births are to mothers in thisage group.
Between 1973 and 1975, the percent of allbirths whose mothers had completed at least 12years of school increased from 69.4 to 71.4 per-cent, reflecting an increase for both racialgroups.
The use of educationzd attainment of motheras a measure of socioeconomic status in relationto birth weight, period of gestation, prenatalcare, interval since last live birth, and illegiti-macy are found in sections that follow.
Education of Father
TabIe 2 shows the percent distribution oflive births by educational attainment of father,age of father, and race. Among all births, 75.9percent were born to fathers with at least a highschool education. The age pattern of this pro-portion was identical to that for mothers.
A larger proportion of white than black in-fants were born to fathers with at least a highschool education (77.5 percent and 64.1 percent,respectively). This was true for every age-of-father category except that of 15-19 years wherethe proportion was identical (48.6 percent) forboth white and black births. The racial differ-ential was great est among infants b om to olderfathers.
A comparison with educational attainmentof mother (table 3) shows that a greater propor-tion of fathers than of mothers had compIetedat least 12 years of schooling. Although the pro-portion who had completed just 12 years ofschool was greater for mothers than for fathers,this was more than offset by a much larger pro-portion of fathers than mothers who had com-pIeted 16 or more years of schooI.
BIRTH WEIGHT
An infant’s weight at birth has long been re-garded as an indicator of his potential for sur-vival and future growth. The greatest risks ofmortality and morbidity exist for those babieswho are of low birth weight. In 1975, 7.4 per-cent of all infants born were in this category.
Low birth weight is a function of intra-uterine growth retardation as well as durationof pregnancy. Statistics discussed in this sectionmake no distinction between low-birth-weightinfants who were born at term and those whowere born prematurely (before 37 weeks ofgestation). However, it has been pointed outthat with regard to postnatal care for the infant,the distinction is of paramount importance,since the care appropriate for low-birth-weightinfants who are premature may be inappropri-ate or even contraindicated for the full-termlow-birth-weight infant.1 Birth weight as it re-lates to duration of pregnancy is discussed atgreater length in the section, “Period of Gesta-tion,” which follows.
Substantial differences between infants ofthe two major racial groups in weight at birthare well recognized. The median weight forblack infants was 220 grams or about 8 ouncesbelow the median weight for white infants in1975 (table 4). Concomitantly, there was a con-siderably higher incidence of low birth weightamong black infants than among white infants(13.1 percent compared with 6.3 percent) in1975.
Some investigators have noted the persist-ence of this racial differential even after adjust-ments have been made for differences in suchmaternal characteristics as age and parity, socio-economic status, cigarette smoking,2 and pre-pregnant weight.3 Failure to eliminate the
3
Table A. Percent of live births of 2,500 grams or less by age of mother and live-birth order: United States, 1973
racial difference after accounting for thesefactors known to be associated with birth-weight differences suggests that genetic as wellas environmental factors may be affecting theobserved differences.
Information from a national study ofmatched birth and infant death certificates forthe 1960 birth cohort shows that in each birth-weight category below 2,001 grams white babieshave higher neonatal death rates than do babiesof all other races.4 )b This survival advantage atlower birth weights supports the hypothesis thatinfants of other races mature more rapidly atthese lower weights than do white infants. (Seethe section, “Period of Gestation” for furtherdiscussion of this hypothesis.) It appears thatthe average birth weight of infants of races otherthan white may be intrinsiczdly lower than thatof white infants, but a lower average birthweight involves less risk for all other infants.
Still, among white and all other infants alike,death rates are higher among those with lowbirth weight than among heavier babies. At thesame time, many more infants of races otherthan white are in the lighter categories. There-fore, as a population, all other infants are sub-ject to higher average death rates. It has beenshown that elimination of the effects of birth-weight distribution differences between white
bAs used throughout this report the term “all other”refers to the combined grouping of all races other thanwhite.
and all other births reduces much of the overallobserved mortality differentiaL4-6
There were no striking changes in the pro-portion of low-birth-weight infants in the periodfrom 1960 to 1975. This proportion increasedfrom 7.7 percent in 1960 to a high of 8.3 dur-ing the mid-1960’s and has since declined to alevel close to that of 1960 (7.4 percent in 1975).The patterns of change in the level of low birthweight among white and all other births duringthis time were simiIar to that for total births.
Weight-at-birth data for black infants, avail-able since 1969, have generally approximatedthe levels observed for all other infants. In gen-eral, the incidence of Iow birth weight for blackbirths is slightly higher than that for all otherbirths. This is reflected in a somewhat lowermedian birth weight for black infants.
Table 4 shows that there is a substantial dif-ference in weight at birth according to the sexof the child. Regardless of race, the medianweight of male infants is higher than that offemale infants. However, the median birthweight for white females is higher th& thatof black infants of either sex.
Maternal age and live-birth order also are as-sociated with variations in birth weight. The in-cidence of low birth weight is greatest amongmothers under 20 years of age, and to a lesserextent among mothers in the later reproductiveyears. Variations in the incidence of low birthweight by age of mother are also related to thebirth-order distribution within each age group.As can be seen from table A, high-order births
4
to young mothers and low-order births to oldermothers are subject to the highest incidence oflow birth weight. Birth weights are generaUymost favorable when age of mother and birthorder are highly correlated.
Over the years, pIace of residence has per-sisted as a factor in variations in the leveIs oflow birth weight. Table 5 shows that the highestlevels of low birth weight occurred among babiesborn to mothers residing in urban places withpopulations of 10,000 or more within metro-politan counties, while the lowest levels wereamong infants born to mothers residing in thebalance of these counties. This pattern holds forall other births during recent years and for whitebirths in all years except 1975 when the percentof low birth weight was higher in urban areas ofnonmetropoIitan counties. However, for the ear-lier years, the lowest incidence of low birthweight among the all other group was for infantsborn to mothers residing in the balance of non-metropoIitan counties. In attempting to interpretthese statistics, it must be noted that a substan-tial proportion of all other births in the balanceof nonmetropolitan counties during the early tomid-1960’s occurred outside of hospitak and,therefore, probably lacked the more precisemeasuring and reporting procedures available inhospitals.
Education of Mother
The proportion of low-birth-weight infantsamong those born to mothers with less than 12years of education was 61 percent higher thanthe comparable proportion among infants bornto mothers with 12 or more years of schoolingin 1973 (table 6). In general, for each age-of-mother group (with the exception of those atthe extremes of the childbearing ages) the pro-portion of low birth weight declined as educa-tional attainment levels rose.
Among white births it can be seen that byage of mother the IeveIs were 29 to 56 percenthigher among mothers who were not high schoolgraduates than among mothers with more educa-tion. Differences by educational attainmentwere not as great for black births where, withthe exception of the 45-49-year age group, thelevels of low birth weight were 6 to 25 percenthigher among births to mothers who had Iessthan 12 years of schooling.
Although an increase in educational attain-ment was generally accompanied by a decline inthe proportion of low birth weight among whiteas well as black babies, the racial differential inthese proportions generally widened as educa-tiorud attainment increased for both raciaIgroups (table 6). This indicates that increasededucational attainment is a more importantfactor in the reduction of low birth weightamong white than among bIack babies. Forbirths to mothers with less than 12 years ofschool, the level was 70 percent higher for blackbabies than for white babies (14.8 comparedwith 8.7 percent ). Among births to mothers whowere at least high school graduates, the differ-ence was greater (the proportion among blackbirths was 111 percent higher than among whitebirths-1 1.8 compared with 5.6 percent).
The relationship between birth weight andfactors such as interval and outcome of lastpregnancy, legitimacy status, period of gesta-tion, plurality, and prenatal care are discussedin subsequent sections of this report.
PERIOD OF GESTATION
Period of gestation was determined from thedate of the mother’s last norrmd menstrual period(LMP) as reported in 40 States and the Districtof Columbia in 1973. The remaining States re-ported gestation in terms of weeks or months,as determined by the physician’s estimate oflength of pregnancy. The result of this lattermethod is often a substantial heaping at 40weeks of gestation due to the tendency to as-sume that an infant of normal size has had agestation period of 40 weeks. The gestationdata presented in this report are based entireIyon data from the IMP reporting areas sincethese are assumed to be the more accurate gesta-tion data.
From the percent distribution of birthsshown in table B, it can be seen that a verylarge majority of births occurred between 37and 42 weeks of gestation. The proportion ofbirths classified as premature (born before 37weeks of gestation) was more than 2 times asgreat for black infants (16.7 percent) as forwhite infants (7.7 percent).
The incidence of prematurity was highestamong infants born to mothers under 15 years
5
Table B. Percent distribution of live births by period of gesta-tion end race: total of 40 reporting States and the Districtof Columbia, 1973
of age (25.2 percent). It decreased to a Iow of7.3 percent among infants born to mothersaged 25-29 years, and then increased slowly to11.5 percent among those born to mothers 40years and over. The same pattern by age of
mother is seen for both major race groups (figure1). The proportion of births that were classi-fied as premature was higher among black thanamong white births for all age-of-mother groups.
Birth weight is directly reIated to period ofgestation (see figure 2). Median birth weight in-creased with increasing gestation to 41-42 weeksof gestation and then decreased sIightIy for 43weeks or more. Of those births that were pre-mature, 40.6 percent were also of low birthweight while onIy 3.6 percent of fuII-term in-fants were of low birth weight.
Although black babies, in general, weigh lessat birth than do white babies, this was not truefor babies born at gestation intervals of less than36 weeks. The median birth weight of black in-fants born at these shorter gestation intervalswas 80 grams higher than that of white infants;at the longer gestation intervals, the medianweight of white infants was 190 grams higherthan that of black infants. This finding hasbeen corroborated by other investigators, someof whom have hypothesized that at these early
40
All racesl------- ~~i~e
‘-- Black
30
‘\.\
$ \,
; 20“\
& “\‘., ‘\.
./” -
%, ./--
-., --\___ .— -—-- --. -_%,
.-. -”-
%‘.,
10
-------- .-------
0U;Jer 15.19 20-24 2529 30.34 35.39 40 ancl
overAGE OF MOTHER (IN YEARS)
NOTE A p,m,, u,e b,,,h ,, ..< that .,,.,, bcrorc 37 ,w.k, .( gc,t.,,on
llocludc, ,,<,, othm than wh, tc and black
Figure 1. Percent of live births premature by age of mother and race: total of 40 reporting States and the District of Columbia, 1973
6
4,(I2O
Whne
3,500—
3,000
g~u 2,5Wz=&
g t
: 2,000~ ,8az /z 1,500E; ,4’
1,000 //
500
020 25 30 35 40 45
PERIODOFGESTATIONIIPJWEEKS)
Figure 2. Median birth weight by period of gestation and race:
total of 40 reporting states and the District of Columbia,1973
gestation intervals the black fetus matures morerapidly.’
Between 1973 and 1975, there was a de-cline in the percent of births that were pre-mature, from 9.2 to 8.9 percent. Although mostof this was due to the decline in prematurityamong black births, the large racial difference re-mained.
Education of Mother
As shown in table C, premature births weremore likely to occur to mothers with feweryears of education than to mothers who hadcompleted 12 or more years of education. A pre-mature birth was more than twice as likely tooccur to a mother who had less than a highschool education than to a mother with a collegedegree. The lower education categories are moreheavily weighted with mothers from the lowestand highest age groups who are themselves moreprone to give birth prematurely than are womenof the intermediate childbearing ages.
Table C. Percent of live births premature by race and educa-tional attainment of mother: total of 37 reporting Statesand the District of Columbia, 1973
[See Technical Notes ]
Years of school completad Allby mother 1 White Black
Less than 12 years .... .. . ... .. .. ... .. ... .. .. . .. 13.1 10.7 19.812 years or more ..... . .. ... .. . ... .. .. ... . ... .. . 7.7 6.7 14.4
1 Includes races other than white and black.
NOTE: A premature birth ia one that occurs before 37weeks of gestation.
There appears to be no appreciable reductionin the racial differentizd in the percent pre-mature among births to mothers of similar socio-economic status. Overall, this percent was 2.2times as great among black as among whitebirths; among births to mothers with 12 or moreyears of schooling and with less than 12 years,the percent was 2.1 and 1.9 times as great,respectively.
MONTH OF PREGNANCY PRENATALCARE BEGAN
Adequate care received during pregnancy isgenerally accepted as a relevant factor in the re-duction of pediatric and obstetric problems suchas low birth weight, congenital anomalies, fetaland neonatal mortality, and maternal mortality.
Since early care is highly correlated withmore care and the detection of obstetrical prob-lems during early gestation stages can possiblyavert certain adverse pregnancy outcomes, earlypregnancy is generally held to be the optimumtime for initiating prenatal care.
In 1973, the month of pregnancy prenatalcare began was reported on the birth certificatesof 42 States and the District of Columbia. Forthese areas, the largest proportion of all infants(43.8 percent) were born to mothers who begancare in the first 2 months of pregnancy. Nearly
7
60
Whine
40 \
20
0Under 1519 2024 25.29 30.34 35.39 4044 45.49
15
AGE OF MOTHER (IN YEARS)
J 1, I fxlm(40 r, -
~?c’”,Black
-------- .-------------- --------
---.-+
20
n1* 2nd 3rd 4th 5th 6th
b,nhs births b,rths births births b,rth$and
LIVE. BIRTH OROER over
Figure 3. Percent of births to mothers beginning prenatal care during the first 2 months of pregnancy, by age of mother and race and
live-birth order and race: total of 42 reporting States and the District of Columbia, 1973
71 percent of all infants were born to motherswho initiated care during the first 3 months ofpregnancy and only 1.5 percent of all infantswere born to mothers who received no care(table 7). By 1975, there had been only slightchanges in these figures-72 percent of allmothers began care in the first trimester and 1.3percent received no care.
Examination of the distribution of births bythe month of pregnancy prenatal care began forthe two major race groups shows that there wasa substantial difference between the groups withregard to the proportion of births to motherswho started care in the first 2 months of preg-nancy-47. 1 percent of white births comparedwith 28.2 percent of black births. Moreover, theproportion of black births to mothers who be-gan care in the last 3 months of pregnancy wasmore than twice the comparable proportion ofwhite births (table 7).
In addition to the greater delay by mothersof black births in obtaining prenatal care, thetotal lack of prenatal care was higher for thisgroup as well. The proportion of mothers withno prenatal care for black births was slightlymore than 3 times that observed for whitebirths–3.4 percent as compared with 1.1 per-cent.
Table 7 shows that age of mother is an im-portant factor associated with the time of in-itiating prenatal care. For all infants, the pro-portion of births to mothers initiating careduring the first 2 months of pregnancy in-
creased with age of mother through the groupaged 25-29 years; over half (52.5 percent) ofthe births to women in this age group were tothose who initiated care at this time. For wo-men 30 years of age and over, as age increas-
Jed there was a ~eady decline in the proportionof births to women who started care early. Veryyoung mothers experienced the highest percentof no prenatal care, and, to a lesser extent, sodid mothers at the older reproductive ages.These patterns of initiation of prenatal care ac-cording to age of mother were similar for bothmajor race groups (figure 3).
As can be seen from table 8, for each birthorder after the second there was a steady declinein the proportion of births to mothers whostarted care during the first 2 months of preg-nancy. While there was a considerable differencebetween white and black mothers in tjhe time ofinitiating prenatal care, both groups tended todelay care as parity increased (figure 3). More-over, as parity increased, there was a generallyhigher percent of mothers reporting no pre-natal care. It has been suggested that this ispossibly the result of increasing home responsibilities and perhaps greater demand on limitedfinancial resources.8 ““
Percent Low Birth Weight
Among all resident births in States reportingmonth of pregnancy prenatal care began, the in-cidence of low birth weight was lowest when
8
mothers initiated care during the first 2 monthsof pregnancy (6.4 percent). (See table D.) Levelsof Ioy birth weight incrqwed as initiation ofprenatal care was delayed until the 6th month(9.2 percent) then decre=ed for mothers be-ginning care in the last 2 months of pregnancy(about 8.0 percent). The pattern for whitebirths was the same as for total births. Althoughthere was no consistent pattern among blackbirths, the lowest levels of low birth weight forthis group were among births to mothers whostarted care in the last 2 months of pregnancy.
There are large differences in the proportionof low-birth-weight babies born to mothers whoreceived some care and to mothers who receivedno care. The percentage of low-birth-weight in-fants born to mothers who had received somecare was 7.2 as compared with 21.1 percent formothers who had received no care. Examinationof gestation data for mothers who had receivedsome care and mothers who had received no care(available for the 39 States and the District ofCoIumbia which reported b, ~,h date of last
1normal menses and month o pregnancy pre-natal care began) shows that a large proportionof infants in the no-care group were born priorto 37 weeks of gestation. Slightly more than one-quarter (26.1 percent) of all births to mothersreceiving no care occurred at gestation ages ofless than 37 weeks, compared with 8.9 percentof births to mothers receiving some care. For the
Table D. Percent of live births of 2,500 grams or less for eachmonth of pregnancy prenatal care began, by race: total of42 reporting States and the District of Columbia, 1973
It has been noted that the “no-care” category islikely to include mothers who would have ob-tained some care had not the early birth of thechild intervened.g
Education of Mother
As can be seen from table 9, earlier prenatalcare is associated with increased levels of educa-tional attainment. When births are examinedwith regard to those born to mothers who re-ceived less than 12 years of education and tomothers who were at least high school graduates,considerable differences can be seen. The pro-portion of births to mothers who began care inthe first 2 months of pregnancy was 69 percenthigher for mothers who were at least high schoolgraduates than for mothers who were not. Theproportion of births to mothers who had no carewas 2.6 percent for those who completed lessthan 12 years of school compared with 0.7 per-cent for those with 12 or more years of school.
A similar association was evident amongwhite and black births, although differences inthe time of initiation of care according to educa-tional attainment were generally greater forwhite mothers. This was particularly true forcare initiated during the second and third tri-mesters and for no prenatal care. The propor-tions of births to white mothers beginning carein the last two trimesters amd to mothers withno care were nearly 2 to 5 times as great forthose who had less than 12 years of school; thecomparable proportions for black births wereless than twice as great.
The proportion of births to mothers begin-ning care in the first 2 months of pregnancy washigher among white than among black births(1.7 times as great). The racial difference wasreduced appreciably only among births tomothers with 16 or more years of school wherethe proportion for white births was 1.2 timesthat for black births. When these proportions
9
are considered for births to mothers with lessthan 12 years of school as opposed to motherswho were at least high school graduates, theracial difference is the same (1.6 times as greatfor white births).
There were greater variations in racial dif-ferences according to education of mother formothers who began care in the last 2 trimestersof pregnancy and for mothers who had no care.Among births to mothers with less than 12years of school, these proportions were 1.4 to2.4 times as great. These differences widenedto 2.1 to 5.8 times as great among births tomothers with 12 or more years of school.
NUMBER OF PRENATAL VISITS
Another measure of prenatal care, avail-able from the birth certificates of 38 Statesand the District of Columbia in 1973, is thenumber of visits for prenatal care made by themother. The median number of prenatal visitsper birth for all mothers residing in these areaswho received some care was 10.6. The com-parable figures for visits made by white andblack mothers were 10.9 and 8.6, respectively(table 7).
The median number of prenatal visits washighly correlated with the month of pregnancyprenatal care began in the 38 areas that reportedboth items. The median number of prenatalvisits declined as initiation of care was delayed,as can be seen from table E. The relative differ-ence between the median number of visits forwhite and black mothers was greater for thetotal than for any individual month in whichcare began. Therefore, much of the racial dif-ferential in the totaJ median number of visitscan be attributed to the fact that white mothersbegan care earlier than did black mothers.
Differences in the median number of visitsby age of mother and by live-birth order (tables7 and 8) are also related to the differences inthe time of initiating care. The increase in themedian number of visits with increase in age formothers under age 30 is associated with the factthat these mothers started care earlier as age in-creased. The slight but steady decline in themedian number of visits per birth as age ad-
Table E. Median number of prenatal visits, by month of preg-nancy prenatal care began and race: total of 37 reportingStates and the District of Columbia, 1973
vanced for mothers 30 years of age and over isalso related to patterns of prenatal care initia-tion for these women. In addition, for aIlbirths after the second, there was a decline inthe median number of visits as birth order in-creased. This is related to the decline in theproportion of births to mothers starting careearly for each birth order after the second.These relationships by age of mother and birthorder were generally true for both major racegroups.
By 1975, the median number of prenataIvisits had increased to 10.8; there was a largerincrease for black than for white mothers (9. 1and 11.1 visits, respectively, in 1975).
Percent Low Birth Weight
Variations in proportions of low-birth-weight babies according to the amount of pre-nataI care received by the mother are shown intable F. The proportion of low-birth-weight in-fants declined as the amount of care increasedfrom no visits to 13 and 14 visits. The pr~po=tion then rose somewhat for visit levels above 14.
It has been suggested that the logical nature...of the relationship between prenatal care andthe levels of low birth weight is not as direct ascasual examination of the data would indi-cate. 10 The association may be a secondary onesince factors known to be associated with low
10
Table F. Percent of live births of 2,500 grams or less by number as the educational attainment level advancedof prenatal visits and race: total of 38 reporting States andthe District of Columbia, 1973 from 12 years to 16 years or more.
birth weight (such as socioeconomic status, ageof mother, and parity) also infl~uence the receiptof prenatal care. 1
Education of Mother
The median number of prenatal visits roseas the level of educational attainment increasedfor white mothers as well as for black mothersas shown in table G. While the relative differ-ence between the races in the median numberof visits was the same for mothers who com-pleted less than 12 years of school as it was forall mothers, this difference nearly disappeared
Tabla G. M;dian number of prenatal visits by educational attain-ment of mother and race: total of 37 reporting States and
In 1975, the sex ratio of live births was1,054 males per 1,000 females. It has variedlittle from year to year from 1940 to 1975,ranging from 1,047 to 1,059.
It has been estimated that the primary sexratio (defined as the ratio of males per 1,000females at the moment of conception), has aminimum value of 1,10011 and may be as highas 1,600.12 The sex ratio of fetal deaths of 20weeks or more gestation (1,126 in 1973) ishigher than that of live births. A higher ratiofor earIy fetaI deaths (20-27 weeks) than for latefetal deaths (28 weeks or more) implies an evenhigher sex ratio for fetal deaths of less than 20weeks of gestation. These high ratios for fetaldeaths result in a lower sex ratio at birth than atconception.
The sex ratio varies widely by race as in-dicated by the average sex ratio for the years1970-73 as shown in table H. The ratio rangedfrom 1,080 for Filipino births to 1,020 forAmerican Indian births. The ratios for the twomajor race groups were 1,058 for white birthsand 1,028 for black births. The ratio for eachof these two groups varied Iittle from year toyear and was consistently higher for white thanfor black births.
As shown in table J, the sex ratio was higheramong single than among plural deliveries. One
Table H. Sex ratio by race: United States, 4-year averaga,1970-73
Race
I Malesper
1,000females
All races................ .......................... ..................1=
Table J. Sex ratio at birth by race and plurality: United States, 1971-75
[See Technical Notes ]
Race and pluralltyI
1975I 1’73 I ‘E@
llnclude~ races other than white and black.
possible causal factor is the higher sex ratio offetal deaths in plural pregnancies compared tosingle pregnancies (1 ,197 and 1,121, respectively,in 1973).
In general, the sex ratio was inversely relatedto birth order and age of mother (table K). How-ever, when these two variables were cross-cIassified, no consistent pattern emerged bybirth order or age of mother. Previous studiesshowed that birth order has a definite effect onsex ratio at birth; the maternal-age effect, how-ever, results from the correlation between birthorder and age of mother. 12>13
Although the sex ratio varies little on ayearly basis, it varies a great deal from month tomonth, especiall~ among black births. For ex-ample, during 1973 the sex ratio for black birthsranged from 1,000 in March to 1,055 in October.The sex ratio for white births ranged from 1,044in September to 1,067 in November. Figure 4shows an average of the sex ratio by month forwhite and black births for the years 1970-73.Although a large variation exists, no seasonalpattern can be identified. These figures showthat the ratio was always higher for white thanfor black births.
Table K. Sex ratio at birth by live-birth order and age of mother: United States, 1973
0 .Jan. Feb. Mar, ,~ Apr. May June Ally Aug. Sept. Oct. Nov. Dec.
MONTHOFBIRTH
.Figure4. Sexratio bymonth of birth and race: United States, 4-year average, 1970-73
MONTH OF BIRTH
The monthly indexes of births occurring inthe United States during 1960, 1970, 1973,and 1975 are shown in table L. These indexesare the ratios of the actual number of births ina month to the average monthly number for thecalendar year multiplied by 100 and adjusted forthe varying number of days in each month.
In 1975, the monthly indexes showed minorpeaks in February and December, and a majorone in September. Indexes for 1960 showed amore prominent peak for September and adeeper trough for the spring months than wasexhibited for more recent years. The reductionin the degree of seasonali$y can be seen in thedecline of the standard deviation of the monthlyindexes. In 1975, the st~drard deviation was 3.3compared with 5.8 in 1960.
The distribution of births by month of oc-currence tends to be bimodal in the UnitedStates, but there are variations in the amplitudeof the seasonaI curve by- race and by region.Figure 5 shows the variations by race in the
Table L. Monthly indexes of live births and standard deviations:United States, 1960, 1970, 1973, and 1975
Total . .... . . .... .. . ... . .. ... .. 3.3 3.3 4.7 I 5.8
NOTE: Index is the ratio of the actual number of births in amonth to the average monthly number for the year multipliedby 100. Adjustment has been made for the varying number ofdays per month.
13
115UNITED STATES NORTHEAST NORTH CENTRAL SOUTH WEST
(Rat,o of number of broths m the month to the average monthly number for the yew multiplied
by 100. Adjustment has been made for varying number of days per month. )
Figure 5. Monthly indexes of live births, by race: United States and each region, 1973
seasonal patterns for the four geographic re-gions in 1973, using the monthly index. In allfour regions the distribution of black births bymonth shows greater variation, as evidenced bymore prominent peaks and deeper troughs, thandoes that of white births. The standard devia-tions for both groups in each of these, regions in1973 are shown below.
The seasonal patterns for white and blackbirths resembled each other in shape in all re-gions except the West where the seasonality ofwhite and black births differed considerably dur-ing the first half of the year.
ATTENDANT AT BIRTH ANDPLACE OF DELlVERY
The vast majority of live births occurring inthe United States are delivered in hospitals. Ofall live births delivered in 1975, 98,7 percentwere classified as having been deIivered by ph ysi-cians in hospitals. These deliveries included alllive births occurring in hospitals or other institu-tions and births attended by physicians in clinics.
The gap between the proportion of whitebirths and all other births occurring in hospitalscontinued to narrow in 1975 (figure 6). Com-parison of the two major racial groups showsthat 98.9 percent of white births and 98.0 per-cent of black births were delivered by physiciansin hospitals.
Over the years, the increase in hospitalutilization for obstetrical care has resulted in adecline in the proportion of births occurring
14
100
95
90
85
80
0
1 -white ------ ,------ ------#.~ --*. - ------
**H
,4*
,/”~~-.
e-*. *- “
~.
1 i I I I I I 1 I I I I , I
1960 1962 1964 1966 1968 1970 1972 1974 1975
YEAR
, Figure 6. Percent of live births occurring in hospitals, by color: United States, 1960-75I
outside these facilities. Physicians outside ofhospitals delivered only 0.4 percent of all livebirths in 1975. The comparable proportions forwhite and black births were 0.3 and 0.6 percent,respectively. The proportions of midwife-attend-ed births are also at relatively low levels–O.4percent of all births, 0.2 percent of whitebirths, and 1.0 percent of black births in 1975(table 10).
—
Much of the differential that has existed be-tween the rates of hospital utilization for whiteand all other births could be attributed to dif-ferences among all other births by place ofresidence. In 1960, 99.1 percent of white birthsand 94.5 percent of all other births in urbanplaces with populations of 10,000 or more weredelivered by physicians in hospitals. In contrast,during the same year, 98.3 percent of whitebirths and only 68.0 percent of births of aIIother races in the balance of the country weredelivered by physicians in hospitak. However,place of residence has assumed diminishing im-portance as a factor in the distribution of allother births by attendant. In 1975, 98.8 percentof all other births in urban places of 10,000
residents or more were delivered in hospitals,compared with 96.3 Percent of all other birthsin th”ebalance of the c-ountry.
Rates of utilization of midwives as attendantsfor all other births have also varied a great dealby type of residence and geographic division,and while fairly substantial differences stillexist, there have been large declines for all areas.As can be seen from table 10, for the balanceof the country the proportion of births of allother races delivered by midwives declinedfrom 25.7 percent in 1960 to 2.3 percent in1975. The comparable proportions for urbanareas of 10,000 residents or more were 2.8 in1960 and 0.3 in 1975. The proportion of allother births attended by midwives is highest inthe East South CentraI Division where, in 1973,4.7 percent of all other births were deliveredby midwives. As recently as 1967, the propor-tion was as high as 21.8 percent.
Comparisons of the two major raciaI groupswith regard to differences by place of residenceare not possible before 1969; data on blackbirths by attendant are available only for 1969and later years. However, distributions of black
15
births for more recent years have been verysimilar to the distribution for all other births.
Geographic variations in the proportion ofbirths occurring in hospitals are somewhatgreater for black births than for white births(table 11). During 1973, in all divisions exceptthe West South Central over 99 percent of whitebirths occurred in hospitals. The proportion ofblack births occurring in hospitak was over 99percent in six of the nine geographic divisions.In the three divisions of the South Region, ratesof hospital utilization for blacks ranged from94.6 percent (East South Central) to 98.3 per-cent (West South CentraI).
MULTIPLE BIRTHS
Of the 57,721 live births that occurred inmultiple deliveries in 1973, the overwhelmingmajority were twin births (98.4 percent ). Themultiple birth ratio is the ratio of live births inmultiple deliveries per 1,000 total live births.This ratio has decreased only slightly since theearIy 1960’s, from 20.4 in 1960 to 18.4 in 1973.In 1975, the ratio was 19.2.
As in other years, black mothers were morelikely than white mothers to have a multiplebirth. The multiple birth ratios in 1973 were22.2 for black mothers and 17.7 for whitemothers (table M).
Table M. Ratio of plural live births to total live births by age ofmother and race: United States, 1973
l~nclude~ ~ac= other than white and black.21nc1ude~ births to women under age 15 and age 45 and over.
The proportion of multiple births increasedas age of mother increased through the 35-39-year age group and then decreased slightly formothers aged 40 years and over. In fact, forboth the white and black population the chancesof a 35-39-year-old mother having a. multiplebirth in 1973 were over twice as great as for a15-1 9-year-old mother.
Both white and black births occurring inplural deliveries have a shorter gestation periodand are of lower birth weight than m-e birthsoccurring in single deliveries. Of single whitebirths, 7.2 percent were classified as premature(gestational age of less than 37 weeks) as op-posed to 38.0 percent of phud white births.Comparable proportions for black births were16.1 and 45.0 percent, respectively. A prema-ture infant is more likely to be a low-birth-weight infant and, since a large proportion ofmultiple births are premature, it follows thata large proportion are of low birth weight. Ofthose white infants in multiple deliveries, 52.6percent were of low~b~th weight, more thqn 9times the proportion ~f white infants in sip#q
vihiz
Table N. Median birth weight and percent of live births of 2,500grams or less, by plurality and race: United States, 1973
lcomPuted to nearest 10 gS’aItMOfl eXaCt conversion‘f ‘n-
terval limits from pounds and ounces.
16
deliveries (5.6 percent), as shown in table N.Low-birth-weight infants also were predominantamong black infants born in plural deliveries(63.9 percent). Of black infants in single deliver-ies, only 12.1 percent weighed 2,500 grams orless. The median weight of infants in singledeliveries was 3,330 grams compared with2,430 grams for infants in plural deliveries, adifference of about 2 pounds.
INTERVAL SINCE LAST LIVE BIRTH
The item “date of last live birth” was addedto the U.S. Standard Certificate of Live Birth toprovide information on child spacing. The in-formation provided by this item makes it pos-sibIe to compute intervals between successivebirths, which is valuable in health and fertilityresearch.
In 1973, the date of last live birth was re-ported on the birth certificates of 40 States andthe District of CoIumbia. This item was used tocoihpute the interwd sii-k!e Iast live birth for aIIsecond and higher order births to mothers re-siding in these areas.
The mean interval since the last live birth forall second and higher’ order births was 43.3months. Table O shows that the length of thisinterval was similar for white (43.6 months) andblack (42.4 months) births. Between 1973 and1975, the mean interval increased 1.0 month forwhite births and 2.7 months for black births. Asa result, in 1975 the direction of the racial dif-ference was reversed; the mean interval was 44.6months for white births compared with 45.1months fo~ black births.
Examination of the mean interval since theprevious live birth according to birth ordershows that the interval was shortest for secondbirths (39.2 months), increased with birth orderthrough fifth births (51.2 months), and then de-cIined through the eighth and higher orders. Thispattern was the same for white births as for totalbirths but varied slightly for black births wherethe mean interval increased through the seventhbirth order and then declined for eighth andhigher orders. These patterns remained the samethrough 1975. In 1973, the differences betweenthe two major racial groups in the mean intervalsince the last live birth for a second and seventh
Table O. Mean intewal since last live birth, by live-birth order,age of mother, and race: total of 40 reporting States andthe District of Columbia, 1973
[See Technical Notes]
Live-hi rth order andage of mother
All second and higherorder births .. .. . .... . .. ... .. .. ... .. . .
and higher order births were less than 2 months.For the remainder of the birth orders, however,the mean intervals were 4 to 6 months longer forwhite births than for black births.
The mean interval since last live birth gener-ally increased with age of mother in both majorracial groups. During 1973, for mothers aged 15-34 years these intervals were up to 6 monthslonger for black births than for white births. Atthe remaining age groups, the mean intervalswere 3 to 19 months longer for white births.
At the younger ages, racial differences ininterval since last live birth may reflect a greaterincidence of induced abortion among blackwomen than among white women. For eventhough black women are more likely to be non-contraceptors, the length of their birth intervalsis somewhat longer, as mentioned above. Ac-cording to estimates of numbers of legal abor-
tions in the United States during the period
17
1972-74,14 the abortion ratio for women ofraces other than white was 1.5 times as great asthe ratio for white women. At ages 20-34 years,the ratios were 1.6 to 2.5 times as great forwomen of races other than white.
On the other hand, at ages 35 and above amore important factor in the racial differencemay be the higher proportion of noncontra-ceptors among black women. There is not asmuch difference between abortion ratios forwhite and all other women at older ages (0.9to 1.4) as at the ages mentioned above. In ad-dition, information from the National Surveyof Family Growth15 indicates that 32.4 percentof currently married white women 35-44 yearsof age compared with 48.2 percent of theirblack counterparts were noncontraceptors in1973. This difference in the use of contra-
ceptives was not as great for younger womenand in addition to the abortion clifferencesmentioned above may explain, in part, the re-versal in the direction of the differential.
Between 1973 and 1975, the increases inthe interval since the last live birth were greaterfor black births than for white births of all birthorders and for mothers in all age groups. Al-though the direction of the racial differenceremained the same for most birth orders and agegroups, it reversed for seventh and higher orderbirths and for mothers under 15, and 35-39years of age. In 1975, the intervals for thesegroups were longer for black births than forwhite births, but in 1973 they were longer forwhite births.
When the mean interval since the previouslive birth is examined by birth order in conjunc-
Figure 7. Mean interval since last live birth, by age of mother and live-birth order: total of 40 reporting States and the District of
Columbia, 1973
18
tion with age of mother, as in figure 7, it can beseen that for each birth order the length of theinterval generally increased with age of mother.For mothers 25 years of age and over, the lengthof the interval decreased as parity increased afterthe third birth. For mothers 20-24 years of age,the length of interval decreased from the secondto seventh order, then increased for eighth andhigher orders.
Education of Mother
The relationship between the mean intervalsince last live birth and educational attainmentof the mother is different for white than forblack births (table 12). With increasing years ofschool completed from 12 to 16 or more, themean interval for white births decreased; forblack births, it increased. This was true for allbirth orders.
Spacing has been identified as an importantfactor associated with fetal and infant mortalityrates. These rates have been found to be lowestwhen the interval between two pregnancies is be-
Lween 2 and 3 years, and the highest infant
ortality rates occur when the birth intervalis less than 2 years. 16 Nearly 40 percent of alllow-birth-weight infants compared with sIightlymore than one-fourth of heavier babies in theStates reporting date of last live birth wert bornless than 2 years after a previous birth.
The relatively high incidence of low-birth-weight infants among young mothers of highparity suggests that the interval between birthsmay be a factor associated--with low birthweight. Data in table 13 show that the incidenceof 10w birth weight for each age group washighest among births that occurred less than ayear after a previous birth. On the other hand,the incidence also increased for intervals of 4years or more since the previous Iive birth. Thesevariations were generally the same for whitebirths, but among black births the incidence de-creased as the interval length increased up to 6years and then rose for intervals of 6 years ormore.
The proportion of births occurring less than2 years after a previous live birth was 1.4 timesas great among births to mothers who completedless than 12 years of school as to mothers whowere at least high school graduates. The differ-ence between these two educational groups in
the proportion of births occurring within 2 yearsof the previous birth was smaller for higher birthorders, declining from 1.6 for second births to1.2 for fourth and higher births. This patternwas the same for white and black births, butthere were somewhat smaller differences forwhite births (table 14).
With few exceptions, the proportion of in-fants born less than 24 months after a previousIive birth was higher for black births than forwhite births at all birth orders and educationalattainment levels in 1973. By 1975, this propor-tion was lower for bIack births than for whitebirths among mothers with 13 or more years ofschool.
INTERVAL SINCE TERMINATION OFLAST PREGNANCY AND OUTCOME OF
LAST PREGNANCY
The mother’s previous pregnancy experiencehas been found to be a major factor associatedwith the infant’s chance for survival.a! 17 In1973, data on the outcome of the last pregnancyof the mother were available for the 39 Statesand the District of Columbia which reported thedates of Iast live birth and fetal death. For allbirths resulting from second and higher orderpregnancies, the mean interval since terminationof last pregnancy was 40.4 months. The lengthof this interval was similar for white (40.6months) and black (39.6 months) births.
The mean interval since termination of thelast pregnancy was approximately 1% yearslonger when that pregnancy ended in a live birththan when it ended in a fetal death. Table Pshows that this was generally true for all birthorders. By age of mother, the interval sincetermination of the last pregnancy was from 4months to 3 years Ionger when the last preg-nancy ended in a live birth than when it endedin a fetal death. This difference increased withage of mother. Although these patterns were thesame for births to mothers in both major racialgroups, the difference between the two preg-nancy outcomes was slightly smzdler for blackbirths.
Between 1973 and 1975, there was an in-crease of 1 month in the interval since termina-tion of the last pregnancy, from 40.4 to 41.4months.
19
Table P. Mean interval since termination of last pregnancy byoutcome of last pregnancy, live-birth order, and age ofmother: total of 39 reporting States and the District ofColumbla, 1973
[See Technical Notes I
Live-birth order andage of mother
All second and higherorder pregnancies . .... . ... ... .. .. ....
The proportion of low-birth-weight infantswas about a third higher among births-to womenwhose last pregnancy ended in a fetal death (9.3percent) than among births to women whose lastpregnancy ended in a live birth (7.0 percent).The figures below show that this was true forboth major racial groups.
White BlackLive birth ................ ......... ........... .. 6.0 12.9Fetal death .................................... 8.1 17.2
Table 15 shows proportions of low-birth-weight infants according to interval since ter-mination of the last pregnancy. These data in-dicate that a longer interval is more favorabIe forbirths following a previous live birth than forbirths following a fetal death. Although the pro-
portions of low-birth-weight infants were highestfor births occurring less than a year since a pre-vious pregnancy regardless of the outcome ofthat pregnancy, the proportion among those oc-curring subsequent to a live birth was over 11/2
times the proportion among those occurring sub-sequent to a fetal death.
It may be that the amount of time requiredfor the mother’s reproductive system to recoverfrom pregnancy and childbirth and for the bodyto build up its reserves in preparation for an-other pregnancy is greater following a live birththan a fetal death. In that case, births followinga previous live birth after a relatively short timewould probably be more likely to have an un-favorable outcome than births closely succeed-ing a fetal death.
Among births occurring subsequent to a pre-vious live birth, the proportion of low-birth-weight infants decreased as the interval increasedfrom 12-17 months to 36-47 months and in-creased for interyals of 4 years or more. In con-trast, among births occurring subsequent to aprevious fetal death the level of low birth weightincreased as the interwd increased from 12-17months to 5 years or more.
The range in the Ievel of low birth ‘weight ac-cording to intervals ~was greater arncmg birthsfollowing a live birth than following a fetaldeath. When the pr&%us pregnancy endedjiw%live birth, the proportion of low birth weightamong infants born less than a year since thatbirth was 4 times as great as among infants bornat the most favorable interval, ~6-47 months(20.4 compared with 5.1 percent). On the otherhand, for births occurring subsequent to a fetaldeath the percent of low birth weight amonginfants born within a year since the fetal deathwas less than t%$ice the percent among thoseborn at the most favorable interval, 12-17months (13.0 compared with 7.3 percent).
The relationships for white births were simi-lar to those for total births, but for bla~ckbirthsthere were some differences, The level of lowbirth weight among black infants born less thana year after a previous pregnancy was nearly thesame for infants born subsequent to a fetaldeath (27.4 percent) as for those following alive birth (29.5 percent). In addition, there wereslight differences in the pattern of low birthweight occurring 4 years or more after botha previous live birth and fetal death.
ILLEGITIMACY
In 1973, an estimated 407,300 illegitimatebirths occurred in the United States, accounting
20
for approximately 13 percent of the 3,136,965live births recorded in that year.
National estimates of the number of illegiti-mate births have been prepared annually since1938. These estimates are based on informationentered on the birth certificates of the Statesthat require the reporting of legitimacy status.In 1973, 38 States and the District of Columbiarequired this information. For discussion of-theprocedure used in making natiomd estimatesof illegitimacy, see the “Technical Appendix” ofvolume I of Vital Statistics of the United States.
Illegitimacy data have been tabulated byrace (white and black) since 1969. For yearsprior to 1969, illegitimacy data were tabulatedby color only, necessitating use of the broadercategory “all other” which consists of a.11racesother than white.
The estimated number of illegitimate birthshas increased steadily each year since 1940, withthe exception of 1948. By 1975, the estimatednumber had increased to 5 times the number in1940 (table 16). During the two 10-year periods1940-1950 and 1950-1960, there was a 58-per-
mmitl increase; between -HMO and 1970 the in-crease was even greater, 78 percent. Since 1970,the estimated number of illegitimate births hasincreased at a slower pace, only 12 percent (to1975); however, the majority of this increasehas occurred since 1973 (10 percent between1973 and 1975). The number of illegitimatebirths among the white population increasedbetween 1973 and 1975, following a decreasebetween 1970 and 1972. Tke number of il-legitimate births among all other races con-tinued to increase during this period, but at aslower pace than in previous years.
Two measures commonly used to describethe incidence of illegitimacy are the illegiti-macy rate and the illegitimacy ratio. The rateis defined as the number of illegitimate birthsper 1,000 unmarried women aged 15-44 years. Itis a measure of the probability that an un-married woman wiIl bear a chiId. The illegit-imacy ratio, defined as the number of illegiti-mate births per 1,000 total births, is a measureof the proportion of total births that are classi-fied as illegitimate.
The illegitimacy rate increased from 7.1illegitimate births per 1,000 unmarried womenaged 15-44 years in 1940 to 26.4 in 1970 (tabIe
16). It decreased slightly since then to 24.1 in1974; however, the rate increased to 24.8 in1975. Although the illegitimacy rate for whitewomen followed the pattern just described, therate for all other women has decreased each yearsince 1971.
Estimated illegitimacy rates by age ofmother and color for the period 1940-75 areshown in figure 8 and by age of mother and racefor 1970-75 in table Q. Women in the primechildbearing ages–20-24 and 25-29 years-hadthe highest illegitimacy rates, followed bywomen 15-19 years old; among women 30 yearsand over the rate decreased with age. A similarpattern was found for both racial groups.
In 1940, the rate for all other women wasnearly 10 times as great as the rate for whitewomen (35.6 and 3.6, respectively). During the1940’s, the color differential increased until, by1950, the rate for all other women was nearly12 times as great as the rate for white women.The differential decreased between 1950 and1969, when it was more than 6, due both to themore rapid increase in the rate for white womenduring the 1950’s and to the decline in the ratefor all women after 1960. Between 1969 and1971, the differential increased slightly to justover 7; it remained relatively stable until 1975when it declined to 6.4.
A leveling off or slight decIine in illegiti-macy rates for white women occurred in themid- to late 1960’s for all but the 15-19-year agegroup (see figure 8). Even greater decreases oc-curred between 1970 and 1974, especially forage groups having the highest rates. However,during 1975 rates increased for all white womenexcept for those aged 35 years and over. Ratesfor a.11other women have Ieveled off or declinedslightly in the late 1950’s or early 1960’s for allage groups and generally remained stable up tothe mid-1 960’s (except for the 30-34-year agegroup in which the increase resumed). Beginningin 1965, sharp declines occurred for all agegroups except ages 15-19 years oId.
The second commordy used measure of il-legitimacy, the illegitimacy ratio, is a measure ofthe proportion of births classified as illegitimate.It is easier to compute than the illegitimacy ratebecause the population data for unmarriedwomen needed to caIculate the rate are oftendifficult to obtain. However, the ratio has num-
21
50C
400
300
m
l,ooil
900
800
700
600
. —.—-
*d+e-------- .-~ .
““-7\
..+ “----/“
.“:.: s.,.. ..”:-;”
,100
,t ----- , .--’---- “.8<,’-----.”- -’%..*----,90 ,.- z - 4’ . -A II other, 20.24 yea
\ -.
80 ,. —
A II other, 15.19 yea,
70A II other, 25.29 pat
60●.-
#.-4’
.
so ,’.-
/
.Z-.
4 .,’”
#-.
AH other, 30.34 year.40
,/ ,~’” # . . ..’
. . . . . .. ...!. . . . . . . . . . . . . . -.
30 ,’. . . . . . .
,.. ...”
,’..-
,’0.-.
20
. ...”
. ..”. . .
. . . Whine, 20.24 years
. ...”. ...”
tiWhtte, 25.29 years
. ..” t All other, 3544 yea=. ...”
. ...”10 ..“
Whne, 15.19 years
,...9
/
/Wh,m, 30.34 ve~n
a
7
5
./ . . . . . ...””” ““” ”.-. . . . . . .
4..- . . .
. . . . . . . . . . . .
. ..”. . . .
,/ . ..-
3 LJhite, 35.44 v~8rs. . ./“
,“ . ..””. ...”
. ..”. ...”
. ...”2 . ..”
. . ...”. . . .
. ...’. . . . .
. . .. . ...”
. ...””. ...”
. ...”
I
1940 1950 1960 1965 1970 1975YEAR
\,,.....
\&,‘%-..
--‘.
+ /-
,
...$.
..%.
“%. . .. . .
m
m
lrs
.
Figure 8. Estimated illegitimacy rates, by age of mother and color: United States, 1940-75
22
Table Q. Estimated illegitimacy rates by age of mother and race: United States, 1970-75
~Rates were computed by relating total illegitimate births regardless of age of mother to unmarried women aged 15-44 years.‘Rates were computed by relating illegitimate births to mothers aged 40 years and over to unmarried women aged 40-44 years.
erous shortcomings when used as an anzdytictool. Th6 numerator and denominator of the il-legitimacy ratio are affected by two independentsets of factors. The numerator, the number of il-legitimate births, is determined by the rate of il-legitimacy and the number of unmarried women.The denominator, the total number of births, isinfluenced primarily by factors that affect thelevel of maritaI fertility, such as changes in tim-ing of births and compIeted family size. Ob-viousIy, if these factors change, the ratio willchange even if the numerator remains the same.
The illegitimacy ratio has increased sub-stantially from 37.9 in 1940 to 142.5 in 1975(table 16). Between 1970 and 1975 alone, therehas been a 33-percent increase in the ratio. Theincrease has taken place in spite of a leveling off
26.4
22.438.437.027.113.6
3.5
13.9
10.922.521.114.2
7.62.0
95.5
96.9131.5100.9
71.832.910.4
or, in some cases, a decrease in the illegitimacyrate since the mid-1960’s. A factor responsiblefor the increase in the illegitimacy ratio duringthis period is one that does not itself determinethe incidence of illegitimacy. This factor is thedecline in total, mainly marital, fertWy (affect-ing the denominator). Also responsible for theincrease in the illegitimacy ratio is the risingnumb er of unmarried women, a factor that af-fects the numerator.
There was a Iarge raciaI differential in the il-legitimacy ratio in 1973 as in previous years: theratios for white and black births were 63.9 and457.5, respectively. The racial differential hasincreased since 1969, following a decline duringthe early 1960’s.
Table R shows the estimated illegitimacy
23
Table R. Estimated Illegitimacy rat!os by age of mother andrace: United States, 1973
ratios by age of mother for 1973. The highestratios were found among births to mothersunder age 20 and particularly under age 15,when the proportion of married women and thenumber of legitimate births are both small. Theratio decreased with increasing age of mother upto and including the age group 25-29 years eventhough the illegitimacy rate shows these mothersto be at greater risk of having an illegitimatebirth. The small ratio for births to mothers ofthese ages is a reflection of the larger proportionof married women and the high level of maritalfertility to these women who are in their primechildbearing years. Thus, although the “risk” ofillegitimacy as measured by the illegitimacy rateis high at ages 25-29, the proportion of birthsthat are illegitimate to women of those ages islow. Age patterns by race are, for the most part,similar to those for all women. However, ratiosfor black women are nearly constant for thoseaged 30 or older.
Education of Mother
About 1 out of 4 live births to women re-porting less than 12 years of education was il-legitimate (table S). This high proportion isrelated to the fact that, for the United States asa whole, about 40 percent of mothers in thiseducation group were under 20 years old, com-
Table S. Percent of live births illegitimate by educational attain-ment of mother and race: total of 33 reporting States andthe District of Columbia, 1973
[See Technical Notes ]
Years of school completed I Allby mothar IIWhite Black
16 years or more ... .. .. .... .. .. .... . ... .... .. .. 1.1 0.7 7.7
I Includes ~ace5 other than white and black.
pared with 10 percent of those with 12 or moreyears of education. As previously noted, thereare fewer married women in this age group andthus fewer legitimate births. The proportion ofillegitimate births decreased as educational at-tainment increased, reaching a low of 1.1 per-cent for mothers reporting 16 or more years ofschool.
The proportion of illegitimate births washigher among black than among white womenfor all levels of education. However, the racialdifferential increased as education increased,ranging from 4.3 times as great for black womenat the lowest level of educational attainment(57.4 percent versus 13.4 percent) to 11.0 timesas great at the highest level (7.7 percent versus0.7 percent).
Percent Low Birth Weight
Illegitimate births are more likely to be oflow birth weight than are legitimate births (tableT). In 1973, as in previous years, nearly twice asgreat a proportion of illegitimate (12.8 percent)as legitimate births (6.8 percent) weighed 2,500grams or less at birth. Although the proportionof low birth weight is greater for illegitimatethan for legitimate births for both major racegroups, the difference among black births is lessthan one-half that among white births (24 per-cent versus 60 percent). However, among birthsto younger mothers (white mothers 15 yearsor younger and black mothers 16 years oryounger), there was a slightly higher proportionof low birth weight among legitimate births.
The difference in percent low birth weightby legitimacy status cannot be attributed solely
24
Table T. Percent of live births of 2,500 grams or less by legitimacy status, age of mother, and race: total of 38 reporting States and theDistrict of Columbia, 1973
to the difference in socioeconomic status be-tween these two groups. The percent low birthweight was higher among illegitimate than amonglegitimate births for all educational levek forboth racial groups (table U). The differential wasgreater for white than for black births, rangingfrom 27 to 109 percent among white births andfrom 18 to 46 percent among black births. The
differential increased with increasing levels ofeducation among mothers who had more than 8years of schooling.
Prenatal Care
Mothers of legitimate births are more likelyto seek prenatal care and to seek it at an earlierstage of pregnancy than are mothers of illegiti-mate births (tabIe V). The vast majority oflegitimate births (75 percent) were to motherswho began prenataI care by the third month ofpregnancy, while less than half (39.5 percent)of the illegitimate births were to mothers whobegan care during the first trimester of preg-nancy. Only 1.0 percent of legitimate birthswere to mothers who had no prenatal care, asopposed to 5.2 percent of illegitimate births.The same variations are observed when the dataare examined by race, but the differences aresmaller among black births.
Table U. Percent of Iiva births of 2,500 grams or less by educa-tional attainment of mother, legitimacy status, andrace: total of 33 reportirm States and the District ofColumbia, 1973 -
Table V. Percent distribution of live births by month of pregnancy’ prenatal care began, by legitimacy status and race: total of 33reporting States and the District of Columbia, 1973
[See Technical Notes]
Race and month of pregnancyprenatal care began
Legit-imate
100.0
46.5
28.520.2
3.81.0
100.0
48.228.918.7
3.40.8
100.0
33.825.431.8
6.72.4
-—
legiti-mate
100.0
19.320.241.613.7
5,2
100.0
19.019.739.716.4
5.2
100.0
19.620.743.111.6
5.0
000
REFERENCES
lNationd Institutes of Health: HOW children gSOW.Clinical Resi?arch Advances in Human Growth and De-uelopnzent. DHEW Pub. No. (NIH) 72-166. Public HealthService. Washington. U.S. Government Printing Office,June 1972. p.15.
2Penchaszadeh, V. B., Hardy, J. B., Mellits, E.D., etal.: Growth and development in an “inner city“ popula-tion: An assessment of possible biological and environ-mental influences, II. The effect of certain maternalcharacteristics on birth weight, gestational age andintra-uterine growth. Johns Hopkins Med. ]. 131:11-23,July 1972.
3Niswander, K. R., Singer, J., Westphal, M., andWeiss, W.: Weight gain during pregnancy and prepreg-nancy weight. Association with birth weight of termgestation. Obstet. Gynecol. 33(4) :482-491, Apr. 1969.
4National Center for Health Statistics: A study of in-fant mortality from linked records by birth weight,period of gestation, and other variables, United States,1960 Iive-birth cohort. Vital and Health Statistics. Series20, No. 12. DHEW Pub. No. (HSM) 72-1055. Washing-ton. U.S. Government Printing Office, May 1972.
5National Center for He~th statistics: Selected vitaland heaIth statistics in poverty and nonpoverty areas of19 Iarge cities, United States, 1969-71. Vital and HeatthStat&tics. Series 21, No. 26. DHEW Pub. No. (HRA)76-1904. Health Resources Administration. Washington.U.S. Government Printing Office, Nov. 1975.
6Bergner, L., and Susser, M.: Low birth weight andprenatal nutrition: An interpretative review. Pediatrics46(6) :946-966, Dec. 1970.
7Westphal, M. C., and Joshi, G. B.: The interrelation-ship of birth weight, length of gestation, and neonatalmortality. Clin. Obstet. Gynecol. 7:670-686, Sept. 1964.
8Kane, S. H.: Significance of prenatal care. Obstet.Gynecol. 24(1):66-72, July 1964.
9Terris, M., and Glasser, M.: A life table analysis ofthe relation of prenatal care to prematurity. Am. j. Pub-lic Health 64(9) :869-875, Sept. 1974.
10Terris, M., and Gold, E.: An epidemiologic studyof prematurity. Am.. J. Obstet. GynecoL 103(3) :371-379, Feb. 1969.
11Markle, G- E.: Sex ratio at bfith: v~ues, Vmiance,and some determinants. Demo~aphy 11(1):131-142,Feb. 1974.
12Twer, J. D., ~d Lee, C.: Sex ratio of registeredlive births in the United States, 1942-63. Demography5(1):374-381, Feb. 1968.
13Myers, R. J.: The effect of age of mother and birthorder on sex ratio at” birth. Milbank Mere. Fund Q.32(3) :275 -281, July 1954.
14Tietze, C.: Legal abortions in the United States:rates and ratios by race and age, 1972-74. Fare. Plann.Perspect. 9(1):12 -15, Jan./Feb. 1977.
15National Center for Health Statistics: Contraceptiveutilization among currently married women 15-44 yearsof age: United States, 1973. Monthly Vital Statistics Re-Port. Vol. 25, No. 7, &lppl. DHEW Pub. No. (HRA) 76-1120, Public Health Service. Washington. U.S. Gover-nmentPrinting Office, Oct. 4, 1976.
16Reportof a WHO Scientific Group. Health aspectsof family planning. WHO Tech. Rep. Ser. No. 442, 1970.
17National Institutes of Health: The women and theirpregnancies. Collaborative Perinatal Study of the Na-tional Institute of Neurological Diseases and Stroke.DHEW Pub. No. (NIH) 73-379, Public Health Service.Washington, U.S. Government Printing Office, 1972.p. 185.
27
LIST OF DETAILED TABLES
1. Percent of births to mothers completing 12 or more years of school by live-birth order, aga of mother, and race: total of 41reporting States and the District of Columbia, 1973 .. .. .. ... .. .. .... . ... ... .. .. ... .. .. ... .. .. .... .. .. .... .. . ..... .. .. ... ... . .... . .. ..... .. .. .... .. . ... ... .. .... ... ..
2. Percent distribution of live births by educational attainment of father, age of father, and race: total of 41 reporting Statesand the District of Columbia, 1973 .. ... ... ..... .. . .... . .. .... .. .. ... .. .. .... . ... ... ... . ..... ... .... .. . .... .. . ..... . ... ... .. .. .... .. .. ... . .... .... . .. .... .....................
3. Percent distribution of live births by educational attainment of mother, age of mother, and race: total of 41 reporting Statesand the District of Columbia, 1973 .... . .. .... ... . .... . .. .... .. .. ... .. .. ... .. .. .... . ... .... .. .. .... . .. .... .. .. ... .. .. ... ... .. ... ... . ..... . .. ..... .. . .... .. ....................
4. Median birth weight and percent of live births of 2,500 grams or lees, by race and sex: United States, 1960, 1965, 1970,1973, and 1975 ... .. .. .... .. .. .... . . .... .. ... ... .. . .... .. .. ... ... . .... .. .. ... .. .. ..... . . ..... . .. ... ... .. .... . .. .... .. .. ... .. .. .... .. ... .................................................
5. Percent of live births of 2,500 grams or less, by place of residence and race for metropolitan and nonmetropolitan counties:United States, 1960, 1965, 1970, 1973, and 1975 .. . .. ... .. .. .... .. .. .... . .. .... . ... ... .. .. .... . ... ... ... . ..... . .... .. .. .. .... . .. ..... . .. .... ... .. .... . .. .... ... .. ...
6. Percent of live births of 2,500 grams or less, by age of mother, educational attainment of mother, and race: total of 41reporting States and the District of Columbia, 1973 . ... .. . ..... .. . .... .. .. .... .. .. .... .. .. .... . .. .... . ... ... ... .. .... . .. ..... .. .. .... .. .. .... .. . .... ... . ..... .. .. ...
7. Median number of pranatal visits and percent distribution of births by month of pregnancy prenatal care began, by ageof mother and race: total of 42 reporting States and the District of Columbia, 1973 . .. .... . .. .... .. .. .... ... . .... .. .. .... .. .. ... .. ... . . ... . .... ..
8. Median number of prenatal visits and percent distribution of births by month of pregnancy prenatal care began, by live-birth order and race: total of 42 reporting States and the District of Columbia, 1973 .... .. .. ..... . . ..... . ... ..... ... .... .. .. .... .. . ..... . .... ... ..
9. Percent distribution of live births by month of pregnancy prenatal care began, educational attainment of mother, and
rata: total of 38 reporting States and the District of Columbia, 1973 . ... .. ... ... .. .. .... .. . .... . ... .... . ... ... .. . ...... . .. ... ... . .... .. .. ..... . ... .... .. .. .
10. Percent distribution of live births by attendant and place of delivery, race, and place of residence: United States, 1960,1970, 1973, and 1975 ... . ... ... .. ... .. .. ... .. .. .... .. .. ... .. .. ... .. .. ... .. ... ... ... . .... .. ... .. ... . .... .. .. .... .. . ... ... . .... ... .. .... .. .. ..........................................
11. Parcent distribution of live births by attandant and place of delivery and race: United States and each geographic division,1973 .. .. .. .... . ... .... .. . .... .. .. ... .. ... ... .. .. .... .. . .... .. . .... .. .. ... .. .. .... .. .. .... .. . .... .. .. .... .. . ... .. . .. .... . . ....................................................................
12. Mean intarval since last live birth by live-birth order, educational attainment of mother, and race: total of 38 reportingStates and the District of Columbia, 1973 .... .. .. ... .. .. ... ... .. .. ... .. .... .. .. .... . .. .... .. .. .... .. . ... .. .. .... .. ... ... .. ... ... ... .. .... . ... ... .. . ..... .. ... .... ........
13. Percent of live births of 2,500 grams or less, by age of mother, interval since last live birth, and rata: total of 40 reporting
14. Percent of births occurring less than 24 months since the previous live birth by live-birth order, educational attainment ofmother, and race: total of 38 reporting States and the District of Columbia, 1973 .. .. .... . .. ..... .. .. .... . .... .... . .. .... . ... .... . ... .... .. .. ..... . .
15. Percent of live births of 2,500 grams or less by outcome of last pregnancy, interval since termination of last pregnancy, andrace: total of 39 reporting States and the District of Columbia, 1973 ... .. ... .... . .. .... .. .. ... .. .. ... .. ... ... ... .. .... ... . ..... .. . .... .. ... ... .. .. .... .. ...
Table 1. Percent of births to mothers completing 12 or more years of school by live-birth order, age of mother, and race: total of 41reporting States and the District of Columbia, 1973
[See Technical Notes]
Age of mother and race
Live-birth order
8thandwar
35.5
1St 4thTotal
2d 3d 5th 6th 7th
All racesl ........................................... .......................... 69.4=
36.075.582.877.467.058.9
73.3
70.7-
39.988.393.689.981.975.9
74.4
76.1
23.574.090.588.880.672.4
78.7
69.1=
13.050.478.583.376.969.9
72.2
61.3 54.0 48.0 43.7
15-19 years ............. .......................................... .......................... ..20-24 yaars ......................... .. .................. .............. ........ ................25-29 years ....................................... .................. ..........................30-34 years ................................................. ...................... .... .. ......35-39 years ................................................................... .. ..... .........40 years and over .................................................. .......................
15-19 years ............................................................. ......................20-24 years ......................... ........ .......................... ............ ...... .. ....25-29 years ........................................................ ...................... .....30-34 years ................................................. .................. ........ ........35-39 yeaw ...................................................................................40 years and over .........................................................................
15-19 years ............................................................b................ ......20-24 years .......................................... ...... ................ ...... .............25-29 years ................................ ........ .............. ...... .......................30-34 years ............................................................ .......................35-39 years ........................ .................................. ............ ........ .....40 years and over ............. ............ .................................. ...... ...... ..
30.965.366.257.948.036.5
27.169.082.680.874.561.5
17.147.869.773.169.354.9
*23.139.650.555.253.1
*14.520.730.840.537.3
16.927.339.645.943.4
lIn~l~des races other than white and black.
29
Table 2. Percent distribution of live births by educational attainment of father, age of father, and race: total of 41 reporting States andthe District of Columbia, 1973
Table 3. Percent distribution of live births by educational attainment of mother, age of mother, and race: total of 41 reporting Statesand the District of Columbia, 1973
lcomputed to nearest I o grams on exact conversion of interval from pounds and ounces.
32
Table 5. Percent of live births of 2,500 grams or less by place of residence and race for metropolitan and nonmatropolitan coun-ties: United States, 1960, 1965, 1970, 1973, and 1975
Table6. Percent of live births of 2,500 grams or less, by age of mother, educational attainment of mother, and race: total of 41reporting States and the District of Columbia, 1973
Table7. Madian number of prenatal visits and percent distribution of births by month of pregnancy prenatal care bagan, by age ofmother, and race: total of42reporting States andthe District of Columbia, l973
lJjasedoninfor~ation from 38report@St atesandtheDi strict Of ColUITlbla.Excludes births tomc.ther swithrmvisits.21nclUdes racesother than white aid black.
35
Table8. Median number of prenatal visits and percent distribution of births by month of pregnancy prenatal care bagan, by live-birthorder and race: total of 42reporting States and the District of Columbia, 1973
lBa~ed on information from sgrep~rting States and the District of Columbia. Excludes birthe. to mothers with no visits.
‘Includes races other than white and black.
36
Table9. Percent distribution of live births by month of pregnancy prenatal care began, educational attainment of mother, andrace: total of38reporting States andthe District of Columbia, 1973
lP[aces with 10,000 resldentsm more in 1960 for that year and 10,000 residents ormmein1970 for 1970.75.‘includes all births inhospitals cmmstitutions and births attended by physicians in clinics, Avery Iafge proportion of births in hospitals are attended by physicians.
38
Table Il. Percent distribution of Iivebirths byattendant andplace ofdelivery and race: United States and each geographic division,
Table 14. Percent of births occurring less than 24 months since the previous Iive birth, by live-birth order, educational attainment ofmother, and race: total of 38 reporting States and the District of Columbia, 1973
[ See Technical Notes]
Years of school completed by mother and race Total
27.1
33.633.124.524,024.6
33,224.4
25.4
31.730.023.323.624.5
30.423.5
34.9
39.740.831.026.121.6
40.629.7
2d
27.1
38.437.224.422.823.6
37.423.9
25.6
36.634.423.322.423.5
34.823.2
35.5
47.245.530.725.519.7
45.828.9
Live-birth order
3d
26.5
31.830.524.225.226.3
30.824.6
24.8
30.026.923.024.925.9
27.723.7
34.5
39.240.230.727.026.3
40.029.9
4th
26.6
29.329.124.426.127.4
29.125.0
24.6
27.325.422.925.827.6
26.023.9
34.6
37.237.832.227.522.5
37.731.2
5th
26.7
29.828.824.525.326.0
29.124.8
24.5
27.525.322.825.025.7
26.023.4
34.1
37.236.331.727.827.3
36.531.0
6thand>ver
30.2
33.331.327.727.628.6
32.127.8
28.0
31.327.626.428.229.3
29.227.0
34.5
36.435.732.125.216.2
36.030.9
Table 15. Percent of live births of 2,500 grams or less by outcome of last pregnancy, interval since termination of last pregnancy, andrace: total of 39 reporting States and the District of Columbia, 1973
[See Technical Notes]
Outcome and interval since last pregnancy
All live births resulting from second and higher order pregnancies .. .. ... .. . ... . .. .... .. .. ... .. .... . .. ... . .. ... .. . ..
1 Because estimates were rounded to the nearest hundred, figures by race may not add to totals.2Rates were computed by relating total illegitimate births regardless of age of mother to unmarried women 15-44 years.
NOTE: The illegitimacy rates shown in this table for the years 1951.68 differ from those published m issues of Viral Statistics of the United States prior to 1969. Therates shown here are based on a smoothed series of popukdirm estimates for unmarried women by race and age, which were not available when the prewously published rateswere computed.
I. Areas reporting educational attainment of parents, dates of Iastlive birth rmdfetal death, datelastnormal menses began (IMP), month of pregnancy prenatal care began, number of prenatalvisits, and Legitimacy status: each State, 1973-75 ... .. ... .. . .. .... . .. ... . .. ... .. . .... . .. .... . . .... . .. ... .. .. ... .. . .. .. .. .. .. 47
45
APPENDIX
TECHNICAL NOTES
Sources of Data
Statistics presented in this report are basedon information from certificates of live birthfiled throughout the United States. Additionaldata and details concerning the technical aspectsof birth statistics are published annually by theNational Center for Health Statistics in volumeI of Vital Statistics of the United States. Table Ishows areas reporting specific items on the certi-ficates of live birth.
Sampling Rates
Data for years prior to 1951 and for 1955are based on the total file of birth records. Datafor 1951-54, 1956-66, and 1968-71 are derivedfrom 50-percent samples of birth records; datafor 1967 are based partly on 20-percent andpartly on 50-percent samples. Data for 1972-75are based on information from two sources. For6 States in 1972, 9 States in 1973, 16 States in1974, and 23 States in 1975, statistics are basedon information from the total file of recordsprovided to the National Center for HealthStatistics through the Cooperative Health Statis-tics System. In 1972, these States were Florida,Maine, Missouri, New Hampshire, Rhode Island,and Vermont. In subsequent years, additionalStates were added as follows: 1973–Colorado,Michigan, New York (exclusive of New YorkCity); 19 74–Illinois, Iowa, Kansas, Montana,Nebraska, Oregon, South Carolina; 19 75–Maryland, Virginia, North Carolina, Tennessee,Louisiana, Oklahoma, and Wisconsin. Statisticsfor the remainder of the United States are basedon information obtained from a 50-percentsample of microfilm copies of all certificates oflive birth.
Residence Classification
M data included in this report are tabulatedby place of residence. Births to U.S. residentsoccurring outside this country have not been re-allocated to the United States. Beginning in1970, births to nonresidents of the UnitedStates occurring in the United States have beenexcluded from tabulations by place of residence.Prior to that year, births occurring in the UnitedStates to nonresident mothers were considered,as births to residents of the place of occurrence.All tables showing time series include data forAlaska beginning with 1959 and for Hawaii be-ginning with 1960.
Geographic Divisions and Regions
The nine geographic divisions (as defined bythe U.S. Bureau of the Census) and their com-ponent States are as folIows:
Division States included
New England. . . . . . . .Maine, New Hampshire,Vermont, Massachusetts,Rhode Island, Connec-ticut
Middle Atlantic. . . . . .New York, New Jersey,
East North Central .,
West North Central . .
South Atlantic. . . . . .
Pennsylvania.Ohio, Indiana, Illinois,Michigan, Wisconsin.Minnesota, Iowa, Mis-souri, North Dakota,Nebraska, Kansas
.Delaware, Maryland, Dis-trict of Columbia, Vir-ginia, West Virginia, NorthCarolina, South Carolina,Georgia, Florida
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Table 1. Areas reporting educational attainment of parents, dates of last live birth and fetal death, date last normal menses began (LMP),month of pregnancy prenatal care began, number of prenatal visits, and legitimacy status: each State, 1973-75
Dates Date last Month ofof last normal pregnancy Number
live birth menses prenatal of prenataland fetal began care visits
death (LMP) began
EducationalArea attainment
of parents
Legitimacystatus
x
x
Alabama
Alaska xI t I
x x
Arizona lx xl xl xl xl x
Arkansas I I I I I x
California I xl xl xl I
Colorado x
Connecticut x
x x x x x
x x x
xl xl xl xl xDalaware lxDistrict of Columbia lx xl xl xl xl x
Florida lx xl xl xl xl x
lx I xl xl xlGeorgia lx
xl xl xl xl xHawaii lxIdaho I
4 xl xl xl xIllinois lxx x x x xIndiana
lx
x x x x x
x x x x x
Iowa x
Kansas x
x x x x x
x x x x
Kentucky x
Louisiana x
x x x x xlx x x
Maine x
Maryland lx
2X
x x x x x
x x x x x
x x x x x
x x x x x
Massachusetts x
Michigan x
Minnesota lx
Mississippi x
Missouri x
See footnotes at end of table.
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Tablel. Areas reporting educational attainment ofparents, dates oflastlive binhand fetal death, date last normal manses began (LMP),month of pregnancy prenatal care began, number of pranatal visits, and Legitimacy status: each State, 1973-75-Con.
IEducational
Area attainmentof parents
Montana I x
Nebraska lxNevada x
New Hampshire x
New Jersey I x
New Mexico INew York lxNorth Carolina lx
North Dakota I x
Ohio x
Oklahoma x
Oregon x
Pennsylvania
Rhode Island x
South Carolina x
South Dakota x
Tennessee x
Texas
Utah I x
Vermont x
Virginia x
Washington
West Virginia x
Wisconsin
Wyoming x
Dates Date last Month ofof last normal pregnancy Number
live birthLegitimacy
menses prenatal of prenatal
and fetal beganstatus
care visits
death (LMP) bagan
x x x x
xl xl xl xl x
x x x x
x x x x x
xl xl xl xl x
xl xl xl Id xl d d x
x x x I x x
x x x
x x x x x
x x x x x
x
x x x xl x
x x x x x
x x x x x
x x x x x
x x
xl xl xl xl x
x x x x
x x
x x x x x
x x x x x
1 xl xl x
x x x I x x
lDid not report in 1973.Zcertificate ~equests on]y date of last live birth.
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;ast South Central . . .Kentucky,Tennessee, Ala-bama, Mississippi
‘Jest South Central . . .Arkansas, Louisiana, Ok-lahoma, Texas
Jorth Central . . . . . . .East North Central, WestNorth Central
South . . . . . . . . . . . . .SouthAtlantic, East SouthCentral, West South Cen-tral
West . . . . . . . . . . . . . .Mountain, Pacific
Population Bases
Populations used for computing illegitimacyrates for the United States exclude the ArmedForces overseas and persons living abroad but in-clude the Armed Forces stationed in the UnitedStates. Rates for 1940 and 1950 are based onthe population enumerated as of April 1 in thecensuses of those years. Rates for all other yearsare based on the estimated midyear (July 1)population for the respective years. For furtherdiscussion see appendix I of the report, Vitaland Health Statistics, “Trends in Illegitimacy,United States, 1940-1965,” Series 21, Number15, from the National Center for Health Statis-tics.
Race and Color
In all cases, race or color refers to the child.Tabulations by color have two categories–“white” and ‘WI other.” Tabulations by raceshow data separately for the black population.
000
+ U, S. GOVERNMENT PRNITNG OFFICE :1978 260-937/21
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VITAL AND HEALTH STATISTICS Series
Series 1. Programs and Collection Procedures. –Reports which describe the general programs of the NationalCenter for HeaIth Statistics and its offices and divisions and data collection methods used and includedefinitions and other material necessary for understanding the data.
Series 2. Data Evaluation and Method~ Research. –Studies of new statistical methodology including experi-mental tests of new survey methods, studies of vital statistics collection methods, new analyticaltechniques, objective evaluations of reliability of collected data, and contributions to statistical theory.
Series 3. Analytical Studies. –Reports presenting analytical or interpretive studies based on vital and healthstatistics, carrying the analysis further than the expository types of reports in the other series.
Series 4. Documents and Committee Reports. – Final reports of major committees concerned with vital andhealth statistics and documents such as recommended model vital registration laws and revised birthand death certificates.
Series 10. Data From the Health Interview Survey .-Statistics on illness, accidental injuries, disability, use ofhospital, medical, dental, and other services, and other health-related topics, all based on data collectedin a continuing national household interview survey.
Series 11. Data From the Health Examination Survey and the Health and Nutn”tion Examination Survey. –Datafrom direct examination, testing, and measurement of national samples of the civilian noninstitu-timsalized population provide the basis for two types of reports: (1) estimates of the medically definedprevalence of specific diseases in the United States and the distributions of the population with respectto physical, physiological, and psychological characteristics and (2) analysis of relationships among thevarious measurements without reference to an explicit fkite universe of persons.
Series 12. Data From the Institutionalized Population Surveys. –Discontinued effective 1975. Future reports fromthese surveys will be in Series 13.
Series 13. Data on Health Resources Utilization. –Statistics on the utilization of health manpower and facilitiesproviding long-term care, ambulatory care, hospital care, and family planning services.
Series 14. Data on Health Resources: Manpower and Facilities. –Statistics on the numbers, geographic distri-bution, and characteristics of health resources including physicians, dentists, nurses, other healthoccupations, hospitals, nursing homes, and outpatient facilities.
Series 20. Data on Mortality. –Various statistics on mortality other than as included in regular annual or monthlyreports. Special analyses by cause of death, age, and other demographic variables; geographic and timeseries analyses; and statistics on characteristics of deaths not available from the vital records based onsample surveys of those records.
Series 21. Data oh Natality, Marriage, and Divorce. –Various statistics on natality, marriage, and divorce otherthan M included in regular annual or monthly reports. Special analyses by demographic variables;geographic and time series analyses; studies of fertility; and statistics on characteristics of births notavailable from the vital records based on sample surveys of those records.
Sm”es 22. Data Frorrs the National Mortality and Natality Survey s.-Discontinued effective 1975. Future reportsfrom these sample surveys based on vital records will be included in Series 20 and 21, respectively.
Series 23. Data From the National Survey of Family Growth. –Statistics on fertility, family formation and dis-solution, family planning, and related maternal and infant health topics derived from a biennial surveyof a nationwide probability sample of ever-married women 15-44 years of age.
For a list of titles of reports published in these series, write to: Scientific and Technical Information BranchNational Center for Health StatisticsPublic Health ServiceHyattsville, Md. 20782
NCHSus Department oF HEALTH EDUCATION AND WELFARE PC)ST HC, E AND FE E5 pAID
Pub!,, Health Sew,Ce US DEPARTMENT OF HEW
Nar,on.1 Ce”mr for Healrh S,,,, S,,., HEW 390
3700 East Wt.S( H,qhw,”Hv.mvlle. Maryland 20782 THIRD CLASS
