Sot. SC;. Med. Vol. 32, No. 6, pp. 715-723, 1991 Printed in Great Britain. All rights reserved 0277-9536191 $3.00+ 0.00 Copyright ‘c 199 I Pergamon Press plc DELAYED ANTENATAL CARE: DOES IT EFFECT PREGNANCY OUTCOME? PETER THOMAS,'JEANGOLDING'.* and TIMJ. PETERS? ‘Research Assistant and *Reader in Child Health, Department of Child Health, University of Bristol, Bristol BS8 ITH, U.K. and %scturer in Medical Statistics, Department of Medical Computing and Statistics, University of Wales College of Medicine, Cardiff, Wales Abstract-Information on 13,127 mothers who were certain of the date of their last menstrual period (LMP) and who delivered in one week of April 1970, was analysed to assess whether delayed attendance for antenatal care (defined as not attending prior to 28 weeks of gestation) was associated with adverse outcome of pregnancy. Background factors that had been found to be predictive of delayed attendance were as follows: region of residence, region of birth of the child’s father, marital status and contraceptive use in the 18 months prior to conception for primigravidae and the same four variables together with parity, maternal age and interpregnancy interval for multigravidae. Both before and after these factors had been taken into account, there was no evidence of any association between delay in attendance for care and severe pre-eclampsia, perinatal mortality, pre-term delivery and birthweight, although after adjustment for the background factors the length of gestation in delayed attenders was, on average, 2 days longer. Key words-delayed antenatal care, perinatal mortality, low birthweight, pre-eclampsia. INTRODUCIION In the late 1980s and early 1990s antenatal care comprises many components ranging from direct screening of the fetus in order to detect abnormalities (amniocentesis, ultra-sound) to monitoring of abnor- malities in the mother which may be predictive of either poor fetal outcome (Rhesus antibodies, high serum alphafetoprotein) or severe maternal disease (pre-eclampsia). The antenatal care clinic is also a source of advice and reassurance to the expectant mother and a place to meet other women in the same situation. Alleviation of fears and a reduction in stress may have a beneficial effect on the mother and fetus. However, these procedures may also have un- wanted effects. For example, amniocentesis is known to occasionally damage a normal fetus or result in miscarriage; knowledge that there is a high alpha- fetoprotein level may result in psychological stress in the mother; pressure to stop smoking may increase her anxiety [ 11. Notwithstanding this, it is generally agreed that the expectant mother will benefit from antenatal obstetric care and will’benefit most if she first attends early in pregnancy, since this enables problems to be detected earlier and enables the pregnant woman to be given the care thought to be appropriate to her obstetric and social background as soon as possible. However, two studies from Aberdeen [2,3] have shown that even when women attended early, and the midwife had taken a clear history, obstetricians frequently failed to take note of facts which should have dictated particular types of care. *Address correspondence to: Dr Jean Golding, Department of Child Health, Royal Hospital for Sick Children, Bristol BS2 8BJ, U.K. An ideal format of antenatal care is still the subject of intense debate carried out, in our opinion, in the absence of sufficient information. A general prac- titioner and an obstetrician [4] have outlined pro- posals for shared care which entail a total of 18 antenatal visits for a mother who goes to term! In contrast, Hall and colleagues [3] after the first Aberdeen study recommend only 6 visits for a normal multipara and 10 for a normal primipara. Everyone appears to be in agreement, however, that the first visit should take place in the first trimester. With no specific prior hypotheses, there are two aims to the present study. The first is to identify the characteristics of women who failed to attend for antenatal care before the end of the second trimester of pregnancy. Having identified their particular back- grounds, we shall then take these into account in assessing whether the fetuses appear to be put at risk by such delay in care. This is done using data on the pregnancies of 13,127 women who were studied as part of the 1970 British Births Survey. The type of antenatal care available and the profile of women who use the facilities has already been described in one of the original reports on the survey [5]. How- ever, given the current discussions on antenatal care it seems pertinent to return to this valuable data resource and to reanalyse it from the perspective of delayed care. It should be noted though that it is unlikely that an observational study will ever be able to identify the ideal quantity and quality of antenatal visits (the two are not synonymous). This is a proper topic for a series of randomised controlled trials. MATERIAL The British Births Survey [5,6] was a study of all births occurring in the week Sth-1 lth April 1970 SSM 32/6-C 715
Transcript
Sot. SC;. Med. Vol. 32, No. 6, pp. 715-723, 1991 Printed in Great Britain. All rights reserved
DELAYED ANTENATAL CARE: DOES IT EFFECT PREGNANCY OUTCOME?
PETER THOMAS,'JEANGOLDING'.* and TIMJ. PETERS?
‘Research Assistant and *Reader in Child Health, Department of Child Health, University of Bristol, Bristol BS8 ITH, U.K. and %scturer in Medical Statistics, Department of Medical Computing and
Statistics, University of Wales College of Medicine, Cardiff, Wales
Abstract-Information on 13,127 mothers who were certain of the date of their last menstrual period (LMP) and who delivered in one week of April 1970, was analysed to assess whether delayed attendance for antenatal care (defined as not attending prior to 28 weeks of gestation) was associated with adverse outcome of pregnancy. Background factors that had been found to be predictive of delayed attendance were as follows: region of residence, region of birth of the child’s father, marital status and contraceptive use in the 18 months prior to conception for primigravidae and the same four variables together with parity, maternal age and interpregnancy interval for multigravidae. Both before and after these factors had been taken into account, there was no evidence of any association between delay in attendance for care and severe pre-eclampsia, perinatal mortality, pre-term delivery and birthweight, although after adjustment for the background factors the length of gestation in delayed attenders was, on average, 2 days longer.
Key words-delayed antenatal care, perinatal mortality, low birthweight, pre-eclampsia.
INTRODUCIION
In the late 1980s and early 1990s antenatal care comprises many components ranging from direct screening of the fetus in order to detect abnormalities (amniocentesis, ultra-sound) to monitoring of abnor- malities in the mother which may be predictive of either poor fetal outcome (Rhesus antibodies, high serum alphafetoprotein) or severe maternal disease (pre-eclampsia). The antenatal care clinic is also a source of advice and reassurance to the expectant mother and a place to meet other women in the same situation. Alleviation of fears and a reduction in stress may have a beneficial effect on the mother and fetus.
However, these procedures may also have un- wanted effects. For example, amniocentesis is known to occasionally damage a normal fetus or result in miscarriage; knowledge that there is a high alpha- fetoprotein level may result in psychological stress in the mother; pressure to stop smoking may increase her anxiety [ 11.
Notwithstanding this, it is generally agreed that the expectant mother will benefit from antenatal obstetric care and will’benefit most if she first attends early in pregnancy, since this enables problems to be detected earlier and enables the pregnant woman to be given the care thought to be appropriate to her obstetric and social background as soon as possible. However, two studies from Aberdeen [2,3] have shown that even when women attended early, and the midwife had taken a clear history, obstetricians frequently failed to take note of facts which should have dictated particular types of care.
*Address correspondence to: Dr Jean Golding, Department of Child Health, Royal Hospital for Sick Children, Bristol BS2 8BJ, U.K.
An ideal format of antenatal care is still the subject of intense debate carried out, in our opinion, in the absence of sufficient information. A general prac- titioner and an obstetrician [4] have outlined pro- posals for shared care which entail a total of 18 antenatal visits for a mother who goes to term! In contrast, Hall and colleagues [3] after the first Aberdeen study recommend only 6 visits for a normal multipara and 10 for a normal primipara. Everyone appears to be in agreement, however, that the first visit should take place in the first trimester.
With no specific prior hypotheses, there are two aims to the present study. The first is to identify the characteristics of women who failed to attend for antenatal care before the end of the second trimester of pregnancy. Having identified their particular back- grounds, we shall then take these into account in assessing whether the fetuses appear to be put at risk by such delay in care. This is done using data on the pregnancies of 13,127 women who were studied as part of the 1970 British Births Survey. The type of antenatal care available and the profile of women who use the facilities has already been described in one of the original reports on the survey [5]. How- ever, given the current discussions on antenatal care it seems pertinent to return to this valuable data resource and to reanalyse it from the perspective of delayed care.
It should be noted though that it is unlikely that an observational study will ever be able to identify the ideal quantity and quality of antenatal visits (the two are not synonymous). This is a proper topic for a series of randomised controlled trials.
MATERIAL
The British Births Survey [5,6] was a study of all births occurring in the week Sth-1 lth April 1970
SSM 32/6-C 715
716 kiER THOMAS el al.
throughout the United Kingdom. Questionnaires were completed by the midwives responsible for the deliveries, and the study included over 98% of all births occurring at that time. Infonnation on live- births was collected for the first 7 days of life.
Included in the questionnaire were details of the total number of antenatal visits, the dates of the first and last visits, and details describing the personnel who undertook the antenatal care.
For the present study we compared two groups of women: (a) those who had had at least one visit for antenatal care before the 28th week of gestation, (b) those who had not visited prior to 28 weeks gestation. Only women with singleton deliveries were con- sidered.
Since duration of gestation was used as a basis for defining our study groups, the 858 women (5.1% of singleton deliveries) with no available information on their LMP date and a further 2355 women (14% of singleton deliveries) who were uncertain of their LMP date were excluded. When there was evidence that dates were dubious [7], these cases were also omitted, even where the mother was confident of her dates. This last category included women whose LMP was either after the date of the first visit for antenatal care or before the date of the last delivery, and in total comprised less than 3% of singleton deliveries.
Definitions used
Gestation: measured in completed weeks from the first day of the LMP.
Gravidity: Number of previous pregnancies re- gardless of outcome.
Interpregnancy interval: Length of time from the end of the immediately preceding pregnancy to the first day of the LMP prior to the study pregnancy.
Marital group: Married: women who were married not later than two months into their pregnancy and were still married at delivery; Premarital conception (PMC): women whose marriages occurred more than 2 months after their LMP; Once-Married (OM): women who were separated, widowed or divorced at the time of delivery; Single: women who had never been married.
Maternal age: Age of mother in completed years at the delivery of the child.
Parity: Number of previous pregnancies resulting in either a stillbirth or a livebirth.
Region: The regional classification is that used by the OPCS. The regions are only occasionally identical with Regional Health Authorities. Initial analyses used the 8 standard regions of England (i.e. North, North-West, Yorkshire and Humberside, West Mid- lands, East Midlands, East Anglia, South-West, South-East), in addition to Wales, Scotland and Northern Ireland. These analyses showed that the proportion of women who attended late for antenatal care were similar in 7 of the English regions and Northern Ireland and these were then combined. West Midlands, Scotland and Wales were considered separately.
Social Class was derived from the usual occupation of the father of the child: I: the higher professionals; II: other professionals and managerial; IIINM: skilled non-manual workers; HIM: skilled manual
The methods may be split into those used to find the predictors of delayed attendance and those used to determine adverse outcome of delayed attendance. There were no specific prior hypotheses, so effectively a data sweeping technique has been employed.
Primigravidae and multigravidae have been considered separately throughout in order first to facilitate the multifactorial analysis of past obstetric history. Furthermore, past attendance and experience of antenatal care (issues on which we have no infor- mation) may have an impact on whether attendance was delayed in the study pregnancy.
Predictors of late attenders were identified by the chi-squared test for association being significant at the 1% level (this level was chosen because of the large number of statistical tests being carried out). Factors found to be significantly associated at the 1% level were then divided into logically distinct groups, representing aspects such as the background of the parents, regions of birth and maternal health be- haviour prior to and during the pregnancy.
Next a systematic procedure employing logistic regression methods was used to determine the set of factors that independently predicted delayed attend- ance. The outcome of these regression models was essentially the proportion of mothers attending for their first antenatal visit either late in pregnancy (the third trimester) or not at all. The models were fitted by maximum likelihood methods assuming the bino- mial distribution.
Initially, the regression method was applied to each group of predictor factors separately so as to identify reduced sets of factors which represented the groups adequately in relation to the antenatal care outcome. These were then combined across groups to obtain a final list of factors which were independently associ- ated with the outcome.
Within each application of the logistic regression technique, the effect of each factor was obtained, controlling for all the others in the model. Non- significant factors (P > 0.01) were dropped one by one until the final model was identified. Regrouping of the categories within each factor was also con- sidered. The goodness of fit chi-squared was used to judge whether fitting interactions would improve the final models. Full details of the methodology are given elsewhere [A.
Having determined the factors associated with delayed antenatal care these were then adjusted for in a series of regression models examining the effect of delayed attendance on various outcomes describing the pregnancy and delivery. For continuous out- comes, standard multiple regression was used so that the regression coefficient took the form of an adjusted difference in the mean outcome between the two antenatal care groups. For the binary outcomes, the use of logistic regression yielded an estimate of adjusted odds ratio of the outcome across the two antenatal care groups.
Delayed antenatal care 717
RESULTS
In all, data were available for 13,127 mothers, 50% of whom had commenced antenatal care by 15 weeks and 75% by 20 weeks. Multiparae tended to attend later than primiparae (medians 15 and 14 weeks respectively). In all, 1385 (11%) had not attended for care by 28 weeks (87 of these did not attend at all prior to delivery).
1. Predictors of delayed attendance
Results of the crude comparisons are shown in Table 1. Amongst a long list of possible predictor variables there were 16 that were significant for one or both of the parity groups. The associations were similar, but not always identical, for primigravidae and multigravidae. Associations between delayed at- tendance and maternal height, ABO blood group and Rhesus blood group were not statistically significant.
Primigravidae. Of the 4492 primigravidae, 454 (10.1%) had not commenced care by 28 weeks. Ten factors were significantly associated (at the 1% level)
with delayed attendance for antenatal care. The logistic regression analyses showed that the following factors were all, at some stage in the process, ex- plained by other factors in the model: father’s social class, mother’s social class, maternal region of birth, mother’s age when she left full-time education, ma- ternal age and lowest haemoglobin level.
This left four factors which were highly signifi- cantly and independently associated with delayed care: marital status, father’s region of birth, region of current delivery and whether the mother used contra- ceptives in the 18 months prior to the current con- ception. This main effects model fitted the data adequately and no interactions were deemed necess- ary.
Figure 1 shows the regression coefficients for these four factors before and after adjustment for one another. It can be seen that the association with marital status shows the least change when the other three factors are taken into account.
In summary, the most effective predictor character- istics of primigravidae who do not attend for ante-
Table I. Associations significant at the 1% level
Proportion delaying attendance
Primigravidae Multigravidae % (N) % (N)
Proportion delaying attendance
Primigravidae Multigravidae % (N) % (N)
Region of delivery West Midlands Wales Scotland All others
Mother’s place of birth England Scotland/Wales/N. Ireland Asia Elsewhere
Father’s place of birth England Scotland/Wales/N. Ireland Asia Elsewhere
Mother’s age <l7yr I&l9yr 2&24 yr 25-34 yr 35+ yr
Social class (husband’s occupation) I, II, IIINM IIIM IV, v
Social class (mother’s occupation) I, II, IIINM, IIIM IV, v Housewife, other
Age father left full-time education <l6yr l6yr ,l7yr
Age mother left fill-time education <l4yr l5yr l6yr S17yr
l **P < 0.001, l *P < 0.01, NS P z 0.01. - Not applicable.
718 PETER THoms et al.
(a) (b)
1.0 - Father’s region of birth
1.0 - ChikY’s region of birth
0.5 -
0.0 I ! /f
J OS- +
---- \
ENQL A----+’
,I , 0.0 ’
q
I I
/
OTHR WMID W4LE SCOT WSNI 4SI4
/
;; s
-0.5 - :/ -0.5 -
::
e m ,o -1.0 - -1.0 -
2 8 ‘0 (cl (dl b ,.. _ Marital status ot conception
1.0 f- Use of contraceptives
5 s
Y 0.5 -
1
KEY: ---- Singlr factor model offwits - Effects adjusted for tha othw three factors
Fig. 1. Regression coefficients for the factors in the final model for primigravidae.
natal care until after the end of the second trimester are:
(a) being single, separated, widowed or divorced; (b) living in the West Midlands; (c) not using contraceptives in the 18 months prior
to conception; (d) the father of the child being born outside
England.
Mdtigravidae. Of the 8635 multigravidae, 931 (10.8%) had not attended for care before 28 weeks. All but one of the factors in Table 1 were associated with delayed attendance. On the other hand, all but parity, father’s region of birth, region of delivery, mother’s age, marital status, use of contraception and interpregnancy interval dropped out of the logistic regression analyses. This model was an adequate fit and hence no interactions were included in the model. The details of the magnitudes of these independent associations are shown in Fig. 2.
2. Outcome of pregnancy
Adjusted regression coefficients with 95% confi- dence limits for the relationship between outcome and delayed attendance are shown in Table 2a (for binary outcomes) and Table 2b (for continuous out- comes). There was a slightly lower incidence of antepartum haemorrhage in multigravidae who de- layed attendance but this was not significant at 1%
and there was no such relationship for primigravidae. The incidence of both mild and severe pre-eclampsia was not significantly different between delayed at- tenders and the rest. There was an excess of women with eclampsia among the delayed attenders, but this was not statistically significant for either gravidity group (nor for the two combined).
Multigravidae who delayed attendance were more likely to have labour induced and to deliver in a consultant unit and less likely to be given regional anaesthesia in labour (Table 2a). Primigravidae were less likely to be booked for the particular place in which they delivered.
There was some indication that the mothers who delayed attendance for antenatal care had shorter labours, but that their gestations were, on average, longer. In addition, there was some evidence to suggest that delayed attenders had a lower inci- dence of pre-term deliveries, although this was not statistically significant for either parity group (Tables 2a, b).
Although the mean gestation of the pregnancies of the women with delayed care were longer, both the mean birthweights and the proportion of low birth- weight babies were no different from those expected. Nor were there any significant differences in perinatal mortality. Indeed, there were actually fewer deaths than expected for both primigravidae and multigravi- dae but the odds ratios were not statistically signifi- cant.
0.0 0.0 -
x
-0.5 -
x -l.OL
Delayed antenatal care
(a) (b) 1.0
Pority 1.0 f-
Father’s region of birth
0.5 0.5 -
Chills region of birth Motcrnol ogc
2 SGOT -\ __ _.
+ .\ ’
2 -0.5 -0.5 6
i t
\.g;
?: 0 J -1.0 -1.0
10) Moritol status ot conception ‘.O
MARR /
SWD SNO Pk
(
I-
1) Use of controccptiver
Inter-pregnancy interval
s ? I 2
-1.oL KEY: -- Slnele factor modal dfwta
-Effects adjusted (or the other 111 tactws
Fig. 2. Regression coefficients for the factors in the final model for multigravidae.
719
720 FWER THOM.ei el al.
Table 2a. Adjusted odds ratio (with 95% confidence limits) of binary outcomes across the two antenatal care groups
Primigravidae Multigravidae
No. of cases Odds ratio No. of cases Odds ratio with positive (95% confidence with positive (95% confidence
Outcome outcome limits) outcome limits)
Antepartum haemorrhage
Mild pm-eclampsia’
Severe pre-eclampsia’
Eclampsia
Induction of labour
Delivery in consultant bed
Booked for delivery at place of delivery
Inhalation analgesia
Regional analgesia
Gestation less than 37 weeks
Birthweight less than or equal to $ lb (62537 g)
Perinatal mortality
381
1437
336
78
1257
3180
3193
2705
1696
214
371
72
1.00 NS (0.68, I .48)
1.04 NS (0.82, 1.32)
0.73 NS (0.47. 1.15)
l.30NS (0.62, 2.73)
I .26 NS (I .OO, I .60)
1.22 NS (0.94, 1.60)
0.49 l ** (0.36.0.65)
0.80 NS (0.64, 0.99)
0.87 NS (0.69, I .09)
0.66 NS (0.39, 1.12)
0.94 NS (0.65, 1.37)
0.75 NS (0.35. I .84)
779
1979
399
71
1911
4649
7016
4858
881
383
412
136
0.72 NS (0.54. 0.95)
0.89 NS (0.74. I .07)
0.77 NS (0.53, 1.14)
1.49 NS (0.74. 3.01)
1.30 l * (1.09. 1.54)
1.49 l ** (1.26, 1.77)
0.76 NS (0.59.0.98)
0.87 NS (0.75, I .02)
0.70 l * (0.52.0.93)
0.69 NS (0.48, I .oO)
I.01 NS (0.73, I .40)
0.89 NS (0.50. I .58)
*‘P < 0.01; l **P < 0.001; NS P > 0.01. ‘Maximum diastolic blood pressure of 90 mmHg or over during antenatal period. ‘Maximum diastolic blood pressure of 90 mmHg or over with proteinuria or a maximum of I IO mmHg or over with no
proteinuria during the antenatal period
DISCUSSION
In this study we have compared the group of women who had not attended for antenatal care before 28 weeks gestation with those who had. The use of delayed rather than non-attendance as the variable of interest eliminates the potential bias brought about by women delivering preterm, having a higher perinatal mortality rate and lower birth- weights for their babies than women delivering at term, but because they delivered early had less oppor- tunity to attend for antenatal care.
It may be thought that the data from 1970 is so out of date that it is totally irrelevant to the present day obstetric scene. Obviously since 1970 enormous steps have been made in the detection of fetal abnormality and consequent termination, and ultrasound is help- ful in identifying multiple pregnancies and assessing dates where these are not known. In the present study, however, we have deliberately only considered singleton pregnancies with known dates, thus exclud-
Table 2b. Adjusted mean difference (with 95% confidence limits) between women who delayed attendance for antenatal care and the
rest of the sample
Primigravidae Outcome (n = 4492)
Length of 1st stage of - 29.20 NS labour (min) (-87.2, 28.8)
Length of 2nd stage of -3.67 NS labour (min) (- 7.29, -0.05)
Gestation + 2.24 l * (days) (0.74.3.74)
Birthweight +0.93 NS
(g) ( - 57.91. 59.77)
l *f < 0.01; ***J’ < 0.001; NS P > 0.01.
Multigravidae (n = 8635)
-35.66 l * (-62.56, -8.76)
0.00 NS ( - I .38, I .38)
+I.71 l * (0.67, 2.75) - 18.96 NS
(-60.88.22.96)
ing those women who would today benefit most from antenatal ultrasound.
Furthermore, the bulk of antenatal care still in- volves accurate history taking, monitoring blood pressure, proteinuria and weight gain. Thus, the present study should be highly relevant in assessing whether the stage of pregnancy at which this type of care commences has any detectable influence on the outcome in those women who are certain of their dates. It cannot address the question of the positive or negative effects of more recent advances.
However, the introduction of new technologies and the increasing numbers taking out private health plans in Britain has probably led to differences, regional, social class and otherwise, in the availability of and the quality of antenatal care. In 1970 only 1% of women delivered privately [6] and access to and type of antenatal care was almost certainly more uniform than today. This would tend to add more weight to the results and arguments presented here since access to and type of antenatal care are less likely to confound the analyses.
The pattern of the backgrounds of mothers who delay attending for antenatal care is unlikely to have changed much over time. This is confirmed when we compare our results with those in the literature. In 1970, Robertson and Carr [8] reported on a survey of late bookers in England and Wales which found that the strongest relationships with women booking after 31 weeks gestation included single status and high parity. The latter was also a risk factor for delayed attendance after 28 weeks gestation in Aberdeen [9]. In Aberdeen in 1975, single status was shown to have a major association with failure to book by 20 weeks gestation [lo]. In the South East of England in 1978, women who were of high parity or immigrants were
Delayed antenatal care 721
most likely to present late [ll]. In London, an analysis of ‘poor attenders’ in 1980 (defined as first attending after 17 weeks and/or missing two appoint- ments) showed major associations with maternal youth, single status and ethnic origin outside the British Isles [12]. Primigravidae who conceived out- side marriage but who subsequently married before the delivery were more likely to attend after 28 weeks gestation than their counterparts who were married throughout pregnancy [13]. In France, in both 1972 and 1976 a similar pattern was seen-‘inadequate’ antenatal care being associated with maternal youth, high parity and short birth intervals [14].
The present study has shown precisely these factors together with a number of others to be of importance. The association between failure (or unwillingness) to use contraceptives and delay in uptake of antenatal care suggests a common attitude which may be labelled either ‘careless’ or ‘spontaneous’ depending on one’s point of view. Failure to plan in detail may be the best description. A high incidence of delayed care in the West Midlands may have been the result of a higher proportion of women in this region being given antenatal care by their GP and a lower pro- portion being given hospital antenatal care when compared with the rest of England. Delayed attend- ance was not related to outcome of the last pregnancy after adjusting for other factors in the logistic re- gression model-a finding similar to that of McKin- lay and McKinlay [13].
The analyses have been carried out separately for primigravidae and multigravidae and there were good reasons for doing so. Although the crude relationship between gravidity and delayed attendance is known, we do not yet know whether other factors would have explained it. Looking at the incidence of delayed attendance by parity for each category of the most likely potential confounders-that is, marital status, use of contraceptives and maternal age-shows that women of parity 0 tend to be less likely to delay attendance or antenatal care than women of parity 1, although the differences are small. For example, in married women, the incidence of delayed attendance in women of parity 0 was 6.1% compared with 7.5% in women of parity 1. In single women, the figures were 34.7% and 34.9%, respectively. This is in con- trast with the crude results that showed an increased incidence of delayed attendance in women of parity 0 compared with women of parity 1.
In their seminal Aberdeen study, Hall and col- leagues [3] interviewed health care workers in the early 1980s. While many thought that the production line atmosphere of hospital clinics might distress women and thus lead to elevated blood pressure and over-diagnosis and treatment of pre-eclampsia, the general practitioners and health visitors ‘saw ante- natal care as preventive medicine aimed at producing a healthy mother and a healthy baby. Regular ante- natal visits ensured that a woman’s blood pressure remained normal, her weight gain satisfactory, and that the baby grew sufficiently. These physiological progress checks were seen to be aimed at the detection and prevention of asymptomatic but serious compli- cations such as smallness for gestational age, mal- presentation or pre-eclampsia’. Yet once again we have to ask where the evidence is for a beneficial effect.
Like the 1980 study of poor attenders in London [ 111, we could find no difference in birthweight be- tween the babies of early and delayed attenders and this was true of both adjusted and unadjusted effects. Nor were there any associations with the incidence of low birthweight. There was also no association be- tween perinatal mortality and delayed attendance. This agrees with the findings from the U.S.A.-for example a study from Portland, Oregon [14] which compared the white population belonging to the Kaiser-Permenante Health Plan with the rest of the white reproducing population. Despite the fact that the former group tended to have their first antenatal visit about a month later than the rest, the weights of their babies were on average greater and infant mortality was lower. Nevertheless, in that study the outcome of women booking in the first trimester was consistently better than those booking later.
There were no statistically significant associations with eclampsia or severe pre-eclampsia. It may have been hoped that early detection and treatment of pre-eclampsia in the group who did not delay care would have resulted in less severe conditions.
The only consistent relationship across both gravidity groups was that the gestation in delayed attenders tended to last, on average, 2 days longer. This was not apparent before adjusting for the factors in the relevant model. There are three possible expla- nations for this relationship:
(i) because care had been delayed, clinicians were less likely to believe their dates and so did not induce at term;
(ii) women who book early are more likely to go into preterm labour;
(iii) the risk of preterm labour is increased as a consequence of some of the components of early antenatal care.
Option (i) seems unlikely since the group with delay in antenatal care attendance was about 30% more likely to have labour induced than the early bookers, There are two pieces of evidence that might support option (ii). Firstly, women delaying antenatal care were, in both gravidity groups, over 40% less likely to deliver preterm. However, neither of these associations was significant at the 1% level. Secondly, women with early bleeding are both more likely to book early and go into preterm labour (151. It is conceivable that early antenatal care will result in earlier identification of potentially dangerous compli- cations such as fulminating pre-eclampsia or intra- uterine growth retardation with consequent early induction of labour or elective Caesarean section. Alternatively, it has been shown that vaginal examin- ations stimulate prostaglandin production [ 161 and theoretically could induce preterm labour. Another suggestion is that maternal stress may result in preterm labour [17]. It is possible that this type of relationship, which in itself is associated with poor outcome, may confound the relationship between outcome and delayed care. Anticipation of antenatal examinations or consequences of advice during ante- natal visits (‘you should stop smoking/stop gaining so much weight/put more weight on/rest/take exercise’, etc.) may well result in a stressed mother.
In any study of attendance for antenatal care, potential biases abound. They include the possibilities that women with some complications of early preg- nancy would be more likely to attend early for care or that women who are feeling heavy and unwell are more likely to postpone a first antenatal visit.
To a certain extent we examined the former possi- bility by looking at the association with early bleed- ing in pregnancy. Proportionately fewer women who booked late had a history of early bleeding (4.0% compared with 6.5%), thus supporting the hypoth- esis. It is possible that relationships with such factors, which are themselves associated with poor outcome, may lead to suppression of an association between delayed care and outcome. On the other hand, we have no data with which to test the second hypothesis which would tend to hide a negative effect of early attendance.
The major omission from this study concerns women who were uncertain of their dates or for whom the dates were thought not to be likely to indicate the date of conception (this will include women who had not menstruated since their previous delivery). Using birthweight to estimate gestational age and hence LMP date would have been inappro- priate and would of course, have confounded the outcome analysis on birthweight and gestational age. This group is the subject of a separate study. Never- theless, it is important to stress here that the present results only apply to women who are sure of their dates and cannot be extrapolated to all women. The present day use of ultrasound to determine gesta- tional length may well present a different picture of delayed attendance in women who do not know their dates.
From the data presented here, however, we would query the assertion that early attendance for ante- natal care optimises the outcome of pregnancy. Like Enkin and Chalmers [l] we would plead for a more rigorous assessment of the components of antenatal care with particular emphasis on the hazards as well as the benefits.
Nevertheless, we must offer a word of caution. The present study is observational in nature and relies wholly on the items of information recorded. It cannot be interpreted as though it was a randomized controlled trial. Women who attend early may well do so because of specific signs or worries that they have whereas those who postpone attendance may be more likely to include women who have felt particu- larly well throughout. It may well be that if we had been able to control for such features our results would reveal a beneficial effect of early antenatal care. A randomised controlled trial would be the most effective method to determine the independent effect of delayed care on pregnancy outcome.
It is also pertinent to recall that numbers were too small to assess whether eclampsia occurred signifi- cantly more frequently among the late attenders.
Although we have shown that in general delayed care is of little consequence with regard to pregnancy outcome, there may be specific (small) groups of individuals who do benefit from early care-for example, those pregnancies with fetal abnormalities and multiple pregnancies. The ethics of encouraging late booking are therefore doubtful.
As Redman [I 81 pointed out, “even if the screening of 5000 pregnant women at 28 weeks prevents just one maternal death, most pregnant women would want to be so protected even though in retrospect more than 90% of the visits would have been non- productive”. Nevertheless, antenatal visits should not consist of procedures which are of no or little value and certainly appraisal of the different components of antenatal care (particularly in the first two trimesters) should be scientifically assessed to deiermine their usefulness.
Acknowledgements-The British Births 1970 Survey could not have been carried out without the voluntary cooperation and enthusiasm of midwives throughout the United King- dom. To them, and to the parents of the children, we acknowledge our substantial debt.
The birth survey was carried out under the joint auspices of the National Birthdav Trust Fund and the Roval College of Obstetricians and G;naecologists, with the present study being funded by the Health Promotion Research Trust.
This paper could not have been written without the able assistance of Yvette Coles, Mary Pears, Terry Shenton, Ruth Hanstead, Neil Lancaster and Helen McCusker, sev- eral of whom were funded by the Manpower Services Commission. We are grateful to them all and to Yasmin Iles for typing the manuscript. Jean Golding is a Wellcome Trust Senior Lecturer.
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