Prevention of preterm birth in high-risk patients: The role of education and provider contact versus home uterine monitoring

Donald C. Dyson, MD: Yvonne M. Crites, MD: Deborah A. Ray, MD: and Mary Anne Armstrong, MAb

Santa Clara and Oakland, California

A total of 394 patients were enrolled in a study to assess the effectiveness of an educational preterm delivery prevention program and to determine whether the addition of home uterine monitoring to the program improved results in patients at high risk of preterm labor. Both the educational program and home uterine monitoring were found to increase the percentage of women with preterm labor who sought care while still favorable for long-term suppression, resulting in a decreased incidence of preterm births and

improved outcome when compared with similar high-risk patients who did not participate in these programs. In a randomized, prospective study, addition of home uterine monitoring to the educational program was found to significantly improve outcome in twin gestations but not in singleton gestations. However, the number of singleton pregnancies was too small to rule out possible benefit from home

uterine monitoring in that group. (AM J OSSTET GVNECOL 1991 ;164:756-62.)

Key words: Premature labor, fetal monitoring, prenatal care, tocolysis

Pre term birth remains the main cause of perinatal mortality and morbidity. I Despite the increasing use of tocolytic agents, the incidence of preterm birth has re­mained unchanged.2 The effect of tocolytic therapy has been severely limited because 70% to 80% of patients in whom preterm labor develops do not seek care until they have ruptured membranes or advanced cervical dilation, making long-term successful tocolysis un­likely.3.4 Recognition of the importance of early detec­tion of preterm labor led to development of preterm delivery prevention programs that stressed identifi­cation of high-risk patients, patient education, self­palpation for uterine contractions, and frequent cer­vical examinations.' Although not uniformly success­ful,6. 7 most studies have found this educational approach to be asssociated with a substantial increase in the percentage of patients with preterm labor who seek care while they are still favorable for suppression, with a resultant decrease in the incidence of pre term births.5,8·10

From the Department of Obstetrics and Gynecology, Kaiser Perma­nente Medical Center, Santa Clara: and the Division of Research, Kaiser Permanente Medical Care Program, Oakland.' Supported in part by the Community Service Program of Kaiser Foun­dation Hospitals. Equipment provided by Advanced Medical Systems. Presented in part at the Eighth Annual Meeting of the Society of Perinatal Obstetricians, Las Vegas, Nevada, February 3-6, 1988, and at the Tenth Annual Meeting of the Society of Perinatal Obste­tricians, Houston, Texas, January 23-27,1990. Received for publication May 23, 1990; revised October 2, 1990; accepted November 9, 1990. Reprint requesL\.· Donald C. Dyson, MD, Department of Obstetrics and Gynecology, Kaiser Permanente Medical Center, 900 Kiely Blvd., Santa Clara, CA 95051. 6/1/26704

756

Katz et al. II showed that overt clinical pre term labor is usually preceded by a period of increased uterine activity that is readily detected by tocodynamometry. Subsequent studies showed that daily home monitoring of uterine activity in high-risk patients also appears effective in increasing the proportion of patients with preterm labor who seek care while they are favorable for suppression, with a resultant decrease in the inci­dence of preterm births." 12 However, other studies 13

· 14 questioned whether it was the monitoring, data from the monitoring, or the patient education and nursing contact that was provided with the monitoring service that was responsible for the improved outcome. The purpose of the present investigation is twofold: (1) to document whether implementation of an organized preterm delivery prevention program results in an im­proved outcome in patients at high risk of preterm labor, and (2) with the use of a randomized, prospective design, to assess whether the addition of home uterine monitoring to the preterm delivery prevention pro­gram would further improve outcome.

Material and methods

Between Jan. I, 1986, andJan. 1, 1989, patients who received prenatal care at the Kaiser Permanente Med­ical Center, Santa Clara, Calif., were prospectively as­sessed for the following risk factors: twin gestation, preterm delivery at <34 weeks' gestation after pre­mature labor or premature rupture of membranes in the preceding pregnancy, premature labor requiring parenteral tocolysis but with term delivery in the pre­ceding pregnancy, incompetent cervix with cerclage in place, and nullipara with bicornuate, subseptate, or di-

Volume 164 Number 3

delphic uterus. A total of 253 patients with these risk factors identified before 28 weeks' gestation and with­out evidence of pre term labor in the current pregnancy, were asked to participate in this study. Two patients refused and 251 patients (99%) gave informed consent and were enrolled. At 24 weeks' gestation, all patients received an initial educational session concerning the signs and symptoms of preterm labor, were taught the technique of self-palpation for uterine activity, and were followed up with weekly cervical examinations. All patients were provided monitors (DT-lOO, Ad­vanced Medical Systems, Hamden, Conn.) for home uterine monitoring. According to the protocol ap­proved by the Institutional Review Board of the Kaiser Foundation Research Institute, patients were random­ized into two groups: the home uterine monitoring group, in which the home uterine monitoring tracings were analyzed and used in patient management, and education-palpation group, in which home uterine monitoring tracings were not analyzed or used in pa­tient management. Patients in the education-palpation group routinely transmitted to a monitor in such a way that the nurse could tell which patients had transmitted but could not analyze uterine activity data. On rare occasions, patients in the education-palpation group erroneously transmitted to a different monitor. When this occurred, the protocol was for the nurse to not analyze or respond to the tracing. The charts of all patients in the education-palpation group who expe­rienced preterm labor were reviewed, and in no case did it appear that a patient in the education-palpation group was referred by a nurse for increased uterine activity detected by one of these accidentally unblinded tracings. Patients were not aware of their group as­signments. All patients were initially asked to monitor themselves 1 hour every day and transmit daily. On Jan. 1, 1988, the protocol was changed to twice-daily monitoring and transmission, and patients in the home uterine monitoring group were given the capability of transmitting an emergent tracing at any time. All pa­tients were asked to record the presence or absence of signs and symptoms of preterm labor and the number of contractions by palpation.

All patients were contacted at least 5 days per week by a study nurse to elicit signs or symptoms of preterm labor, record the number of contractions by palpation, and, in the home uterine monitoring group, to review the monitoring information. All patients were in­structed to report to the hospital for evaluation if they had more than five contractions per hour that persisted for more than 1 hour despite lateral bed rest and oral hydration. Asymptomatic patients in the home uterine monitoring group who had more than five contractions per hour on routine monitoring were instructed to lie down, drink fluids, and remonitor for 1 hour. If they

Prevention of preterm birth 757

persisted with more than five contractions per hour they were referred for evaluation.

All patients in this study were evaluated and treated at Kaiser Foundation Hospital, Santa Clara, Calif., with clinical protocols that recommended tocolysis for per­sistent uterine contractions if the cervix was already dilated to 2 cm but otherwise required documented cervical change before tocolysis. Prophylactic tocolytic agents were not administered to any patients in this study. Choice of tocolytic agents used was determined by clinical protocol and physician preference and was neither affected by nor did it differ by study groups. If tocolysis was successful, patients were discharged home to bed rest taking oral tocolytic agents and main­taining their pretreatment group protocols. In the home uterine monitoring and education-palpation groups, the dosage of oral tocolytic agent was adjusted to maintain fewer than six contractions per hour on monitoring and on palpation, respectively. Oral toco­lysis and monitoring were discontinued at 36 weeks' gestation. Patients who were delivered of infants at <36 weeks' gestation were classified as either a result of failed tocolytic therapy or as indicated preterm births. All gestational ages were confirmed by first- or second­trimester ultrasonography.

A group of 143 patients with the same risk factors for preterm labor who received their prenatal care and were delivered of infants at the same hospital in the 30 months immediately preceding the start of the pro­spective study was identified as the standard care group. To avoid adverse selection, particular care was taken to select patients by the presence of the risk factor and not the outcome. The same clinical protocols for assessment and treatment of preterm labor were in ef­fect during both the control and study time periods. In this study, preterm labor was diagnosed only if there were persistent uterine contractions (>5 hours) asso­ciated with either 2 cm of cervical dilation or docu­mented cervical changes. Favorable for suppression was defined as intact membranes and cervix dilated ::s2 cm. Respiratory distress syndrome was diagnosed if there was a neonatal oxygen requirement that lasted >24 hours and a compatible x-ray film of the chest. Statis­tical analysis was performed with the X2 test, the Fisher exact test, or the Student t test, as appropriate. Results are expressed as mean ± SEM. All P values of ::sO. 1 0 were reported in the tables.

Results

A total of 394 patients were enrolled in the study. Four patients (1.6%), two patients each from the home uterine monitoring and education-palpation groups, subsequently elected to drop out of the study, resulting in a total of 247 patients in the randomized study and 143 in the control group. Of these, 189 were twin ges-

758 Dyson et al.

Table I. Pregnancy outcome: singleton gestations

March 1991 Am J Obstet Gynecol

HUM:f: SC vs EP SC vs HUM HUM vsEP Outcome (%J (%) (%) (p value) (p value) (p value)

PTL <36 wk 28.6 34.3 33.8 NS NS NS PTL <34 wk 20.6 27.1 27.9 NS NS NS PTB <36 wk 31.8 20.0 23.5 0.09 NS NS PTB <36 wk, FT 25.4 5.7 13.2 <0.01 0.06 NS PTB <34 wk 23.8 11.4 11.8 0.05 0.06 NS PTB <34 wk, FT 20.6 5.7 7.4 0.01 0.03 NS

EP, Education-palpation group; FT, failed tocolysis; HUM, home uterine monitoring group; NS, not significant; PTB, preterm birth; PTL, preterm labor; SC, standard care group.

*n = 63. tn = 70. :j:n = 68.

Table II. Neonatal outcome: singleton gestations

SC EP HUM SC vs HUM HUM vsEP Outcome (n = 63) (n = 70) (n = 68) (p value) (p value)

Birth weight (gm)* 2767 ± 109 2882 ± 94 2938 ± 93 NS NS NS <2500 31.8% 18.6% 20.6% 0.06 0.10 NS <1500 7.9% 8.6% 5.9% NS NS NS RDS 14.5% 6.0% 8.8% 0.09 NS NS leN admission 29.0% 16.4% 22.1% 0.07 NS NS IHS (days)* 10.9 ± 2.3 5.2 ± 1.4 8.8 ± 2.5 0.04 NS NS

EP, Education-palpation group; HUM, home uterine monitoring group; fCN, intensive care nursery; fHS, infant hospital stay; RDS, respiratory distress syndrome; SC, standard care group.

*Mean ± SEM.

tations and 201 were singleton gestations. Analysis by risk factor in patients with singleton gestations revealed no statistically significant differences in outcome; how­ever, significant differences were found between pa­tients with singleton gestations and those with twin ges­tations. Results are therefore presented separately for singleton and twin gestations.

Singleton gestations. The distribution of risk factors for preterm labor was similar among all three groups of patients. One previous preterm birth was the indi­cation in 63% of the standard care group, 65% of the education-palpation group, and 56% of the home uter­ine monitoring group; two or more previous preterm births was the indication in 17%, 16%, and 23% in the standard care, education-palpation, and home uterine monitoring groups, respectively. The mean number of unscheduled visits to rule out preterm labor was greater in both the education-palpation (1.4) versus the stan­dard care group (0.2, p = 0.01) and in the home uter­ine monitoring (1.8) versus the standard care group (0.2, p = 0.01). The difference between the education­palpation and home uterine monitoring groups was not statistically significant. As shown in Table I, the differ­ence in incidence of preterm labor was not statistically significant when comparing the three groups in pairs; however, the incidence of pre term birth was markedly less in the education-palpation group than in the stan-

dard care group. The incidence of preterm birth also appears to be less in the home uterine monitoring group than in the standard care group, but the differ­ence reached statistical significance only for those de­livered of infants at <34 weeks' gestation, specifically because of failed tocolysis. There was no apparent dif­ference between the education-palpation and home uterine monitoring groups. Table II shows that al­though there were definite trends toward higher birth weights, shorter infant hospital stays, fewer infants ad­mitted to the intensive care nursery, and fewer infants who developed respiratory distress syndrome in both the education-palpation and home uterine monitoring groups when compared with the standard care group, only the shorter infant stay in the standard care versus education-palpation comparison reached statistical sig­nificance.

In all three groups, patients with preterm labor at <34 weeks' gestation had aggressive tocolytic therapy unless there were contraindications. Management of patients with onset of preterm labor between 34 and 36 weeks' gestation was less uniform and was characterized by less aggressive use of tocolytic agents and occasion­ally nontreatment, especially after 35 weeks' gestation. Outcome data are thus reported for both 34 and 36 weeks' gestation. Table III shows indicators of preg­nancy outcome in only those patients with onset of pre-

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Prevention of preterm birth 759

Table III. Patients with singleton gestations with preterm labor <34 weeks' gestation

SC EP HUM SC vs HUM HUM vsEP Outcome (n = 13) (n = 19) (n = 19) (p value) (p value)

GA at PTL (wk)* 29.7 ± 0.9 29.1 ± 0.6 29.1 ± 0.7 NS NS NS GA at delivery (wk)* 30.8 ± 0.6 35.5 ± 0.9 34.7 ± 0.9 <0.01 <0.01 NS Days gained* 7.3 ± 3.6 44.7 ± 6.9 39.2 ± 5.6 <0.01 <0.01 NS Favorable for suppression 30.8% 84.2% 68.4% <0.01 0.04 NS Delay >48 hr 46.2% 89.5% 89.5% 0.01 0.01 NS Delivered >34 wk 0 73.7% 68.4% <0.01 <0.01 NS leN admission 92.3% 36.8% 47.4% <0.01 0.01 NS RDS 69.2% 21.1% 26.3% 0.01 0.02 NS BWT <2500 gm 100% 36.8% 47.4% <0.01 <0.01 NS BWT (gm)* 1566 ± 110 2624 ± 211 2299 ± 174 <0.01 <0.01 NS IHS (days)* 36.4 ± 7.5 10.5 ± 5.0 16.9 ± 6.0 0.01 0.05 NS

BWT, Birth weight; EP, education-palpation group; GA, gestational age; HUM, home uterine monitoring group; IHS, infant hospital stay; PTL, preterm labor; RDS, respiratory distress syndrome; SC, standard care group.

*Mean ± SEM.

Table IV. Pregnancy outcome: twin gestations

HUM:/: SC vs EP SC vs HUM HUM vsEP Outcome (%) (p value) (p value) (p value)

PTL <36 wk 45.0 42.1 48.1 NS NS NS PTL <34 wk 32.5 36.8 42.3 NS NS NS PTB <36 wk 46.3 29.8 23.1 0.05 0.01 NS PTB <36 wk, FT 26.3 14.0 7.7 0.06 0.01 NS PTB <34 wk 28.8 17.5 9.6 NS 0.01 NS PTB <34 wk, FT 22.5 10.5 5.8 0.05 0.01 NS

EP, Education-palpation group; FT, failed tocolysis; HUM, home uterine monitoring; NS, not significant; PTB, preterm birth; PTL, preterm labor; SC, standard care group.

*n = 80. tn = 57.

*n = 52.

term labor at <34 weeks' gestation. A much higher proportion of patients in the education-palpation and home uterine monitoring groups were seen while still favorable for suppression, with a resultant improve­ment in success rate of both short-term (>48 hours) and long-term (delivery after 34 weeks' gestation) sup­pression. Correspondingly, neonatal outcome as mea­sured by birth weight, percent with intensive care nurs­ery admission or respiratory distress syndrome, and duration of infant hospital stay all were significantly improved in both the home uterine monitoring and education-palpation groups as compared with the stan­dard care group. There was no apparent difference

between home uterine monitoring and education­palpation groups in any of the factors in Table Ill.

Twin gestations. There were no statistically signifi­cant differences between groups in the patient demo­graphics including maternal age, gravidity, parity, per­

cent nulliparous, and percent with previous preterm delivery. Table IV shows that whereas the incidence of

preterm labor was similar in all three groups, the inci­dence of preterm birth was decreased in the education­palpation group and markedly decreased in the home uterine monitoring group compared with the standard

care group. The incidence of patients delivered of pre­mature infants as a result of failed tocolytic therapy at <34 weeks' gestation was decreased by 53% in the ed­ucation-palpation group and by 74% in the home uter­ine monitoring group as compared with the standard care group (p = 0.05 and 0.01, respectively). Table V shows that infants in the education-palpation group tended to have a better outcome than those in the stan­dard care group and were significantly less likely to be admitted to the intensive care nursery, develop respi­ratory distress syndrome, and experience neonatal death than were the infants in the standard care group. Infants in the home uterine monitoring group clearly had the best neonatal outcome, having shown highly significant improvements in all indicators of neonatal outcome as compared with the infants in the standard

care group and were significantly less likely to have weighed < 1500 gm, to have been admitted to the in­tensive care nursery, and to have had a shorter hospital stay as compared with the infants in the education­

palpation group. Table VI shows that patients with twin gestations in

whom the onset of preterm labor developed before 34

weeks' gestation had similar gestational ages when that

760 Dyson et al.

Table V. Neonatal outcome: twin gestations

SC EP Outcome (n = 160) (n = 114)

BWT (gm)* 2333 ± 83 2535 ± 87 BWT <2500 gm 52.2% 46.5% BWT <1500 gm 14.5% 8.8% RDS 21.9% 8.8% lCN admission 57.5% 43.9% Neonatal death 7.5% 0.9% lHS (days)* 11.7 ± 1.4 10.2 ± 1.7

HUM SC vs EP (n = 104) (p value)

2687 ± 71 0.09 36.5% NS

1.9% NS 3.9% 0.00

27.9% 0.02 0 0.01

5.6 ± 0.4 NS

SC vsHUM (p value)

0.00 0.01 0.00 0.00 0.00 0.00 0.00

March 1991 Am J Obstet Gynecol

HUM vsEP (p value)

NS 0.09 0.03 0.10 0.01 NS

0.01

BWT, Birth weight; EP, education-palpation group; HUM, home uterine monitoring group; ICN, intensive care nursery; IHS, infant hospital stay; RDS, respiratory distress syndrome; SC, standard care group.

*Mean ± SEM.

Table VI. Patients with twin gestations with preterm labor <34 weeks' gestation

SC vs HUM + EP Outcome SC (p value)

Maternal (n = 26) (n = 21) (n = 22) GA at PTL (wk)* 30.2 ± 0.7 30.0 ± 0.6 31.1 ± 0.5 NS NS NS NS GA at delivery (wk)* 31.1 ± 0.9 33.9 ± 0.8 36.1 ± 0.5 0.02 0.00 0.03 0.00 Days gained* 6.0 ± 2.2 27.4 ± 4.9 34.6 ± 4.3 0.00 0.00 NS 0.00 Favorable for suppression 26.9% 66.7% 95.5% 0.01 0.00 0.02 0.00 Delay >48 hr 34.6% 76.2% 100.0% 0.01 0.00 0.02 0.00 Delivered >34 wk 19.2% 52.4% 81.8% 0.02 0.00 0.04 0.00

Neonatal (n = 52) (n = 42) (n = 44) lCN admission 88.2% 70.7% 41.9% 0.03 0.00 0.01 0.00 RDS 50.9% 24.4% 9.3% 0.01 0.00 0.06 0.00 BWT <1500 gm 40.4% 23.8% 4.6% 0.07 0.00 0.01 0.00 BWT (gm)* 1700 ± 106 2098 ± 112 2476 ± 83 0.01 0.00 O.oI 0.00 lHS (days)* 22.6 ± 3.7 19.6 ± 4.4 6.8 ± 0.9 NS 0.00 0.00 0.03

EP, Education-palpation group; GA, gestational age; HUM, home uterine monitoring group; ICN, intensive care nursery; IHS, infant hospital stay; RDS, respiratory distress syndrome; SC, standard care group.

*Mean ± SEM.

occurred. However, gestational age at delivery was sig­nificantly improved in both the education-palpation and home uterine monitoring groups as compared with the standard care group. Once again, this appeared to be a result of a higher percentage of patients who were seen while still favorable for suppression, result­ing in improved short-term and long-term tocolysis and improved neonatal outcome in both the education­palpation and home uterine monitoring groups. Ta­ble VI also shows that whereas both the education­palpation and home uterine monitoring grou ps showed an improved outcome compared with the standard care group, the home uterine monitoring group had the best outcome; the home uterine monitoring group had a statistically significant improvement in the percentage of patients seeking care while still favorable for sup­pression, in effectiveness of short-term and long-term tocolysis, and in all indicators of neonatal outcome as compared with the education-palpation group.

Comment

The success of tocolytic therapy is highly dependent on the status of the cervix and membranes at the in i-

tiation of tocolysis. 15 Early detection and treatment of preterm labor has been advocated as the key factor in the prevention of preterm births. 5 Unfortunately, studies have suggested that 70% to 80% of women in whom preterm labor develops are seen only after they have ruptured membranes or have advanced cervical dilation, making successful longer-term tocolysis un­likely.3.4 Our study confirms these findings, with 69% of women with singleton pregnancies and 73% of those with twin gestations in our standard care group who ex­perienced preterm labor seeking care when they were no longer favorable for long-term tocolytic therapy.

Our study agrees with previous reports5• 8-lO that sug­

gest that participation in an organized preterm delivery prevention program that emphasizes patient education and frequent provider contact can significantly increase the percentage of high-risk patients in whom preterm labor develops who seek care while still favorable for suppression, thus increasing the success of tocolysis and decreasing the incidence of preterm birth. In our study, the percentage of women with preterm labor who sought care while still favorable for suppression increased from 31 % to 84% in singleton and from 27%

Volume 164 Number 3

to 68% in multiple gestations after initiation of such a preterm delivery prevention program (education­palpation group), and the incidence of preterm birth at <34 weeks' gestation subsequently decreased by 54% in singleton gestations and by 41 % in twins.

Our study also agrees with previous reports" 12 that suggest that daily home monitoring of uterine activity in high-risk patients can also increase the early detec­tion of preterm labor, allowing more successful treat­ment and improved outcome. In our study, the per­centage of patients with preterm labor who sought care while still favorable for suppression increased from 31 % to 68% in singleton and from 27% to 96% in multiple gestations in the home uterine monitoring group, and the incidence of preterm birth at <34 weeks' gestation decreased by 50% in singleton and by 66% in multiple gestations, resulting in a highly sig­nificant improvement in all indicators of neonatal out­come in the home uterine monitoring group compared with the standard care group.

Our study strongly suggests that both the educational approach and home uterine monitoring are effective in the improvement of outcome in patients at high risk of preterm labor. However, in the home uterine mon­itoring group, the question14 as to whether it is the monitoring information or the frequent nursing con­tact that occurs in conjunction with home uterine mon­itoring that results in improved outcome is more dif­ficult to answer. In singleton pregnancies, within the limits of our study design, there was no apparent dif­ference in outcome between the education-palpation and home uterine monitoring groups. However, in pa­tients with twin gestations, use of home uterine mon­itoring information resulted in an increase in those with preterm labor favorable for suppression from 68% to 96% and an increase in the success of both short-term (76% to 100%) and long-term (52% to 82%) tocolysis compared with the education-palpation group. Al­though the 45% reduction in preterm births before 34 weeks' gestation did not reach statistical significance, there was a significant reduction in both births of < 1500 gm and admissions to the intensive care nursery as well as shorter infant hospital stays in the home uter­ine monitoring group compared with the education­palpation group. Thus our study suggests that for pa­tients with a twin gestation, the addition of home uter­ine monitoring information will improve outcome even if they are already participating in an intense preterm delivery prevention program with frequent provider telephone contact.

There are several possible explanations as to why home uterine monitoring was found to be more ben­eficial in twin gestations than in singleton gestations in this study. It has been reported that patients with mul­tiple gestations perceive contractions less accurately

Prevention of preterm birth 761

than do patients with singleton gestations. 16 In multiple gestations, this decreased perception may limit the ef­fectiveness of programs that depend on the mother's ability to perceive or detect contractions. The possible bias of nurses who have occasional accidental knowl­edge of home uterine monitoring data in education­palpation patients is an unlikely explanation of the fail­ure to find a difference in singleton gestation because the same nursing protocols were used with twin ges­tations in which significant improvement was found with home uterine monitoring. The use of six contrac­tions per hour as the threshold, instead of the more commonly used four contractions per hour, is also an unlikely explanation of the failure to find efficacy in home uterine monitoring in singletons because only one patient in the singleton home uterine monitoring group was found to have had between four and six contractions per hour on the last tracing before diag­nosis of pre term labor. However, the design of our study may have acted to minimize the differences in outcome between the home uterine monitoring and education-palpation groups. Patients in the education­palpation group were contacted at least 5 days per week by telephone. This is a much higher standard of care than that found in most preterm delivery prevention programs. Patients in the education-palpation group also received a home monitoring device. Although the monitoring information was not used, presence of a monitor may well have decreased the dropout rate and increased the compliance in the education-palpation group. In addition, the lower rate of preterm labor and the relatively small number of patients in our singleton groups would make it more difficult to detect a true difference. With the size of our singleton groups, to have a power of 80% would require a 75% or larger reduction in preterm births in the home uterine mon­itoring group (20% to 5%), with a two-tailed hypothesis test and a significance level of 0.05. Our numbers are thus too small to reasonably expect to detect a reduction in preterm labor as a result of uterine monitoring of <75% in our singleton groups.

In summary, our patient population consists pre­dominantly of compliant patients from the middle so­cioeconomic class with a relatively low incidence of drug abuse and infection complications, so that these inter­ventions may not be as successful in other dissimilar patient populations. In our study, both an organized preterm delivery prevention program with the use of frequent telephone contact with nurses and a home uterine monitoring program were found to signifi­cantly improve outcome in patients at high risk of pre­term labor compared with our previous standard of care. In our study, the addition of home uterine mon­itoring in patients with twin gestations resulted in im­proved outcome as compared with those patients man-

762 Dyson et al.

aged with frequent tel phone contact with nurses only. The issue of efficacy of home uterine monitoring in singleton pregnancies at high risk of preterm labor re­mains unresolved and awaits further clinical trials. However, our own internal cost analysis suggests that providing the same intense preterm delivery preven­tion program with frequent nursing contact but delet­ing the home uterine monitor would result in only a 17% cost saving. Thus on the basis of our study and others," 8-10 it appears that patients with singleton ges­tations who have major risk factors of preterm labor benefit greatly from participating in a pre term delivery prevention program. If the components of a preterm delivery prevention program (patient education;and frequent provider contact) cannot otherwise be made available to these high-risk patients, which is often the case in clinical practice, then home uterine monitoring may be a reasonable alternative. From our study, it also appears that home monitoring of uterine activity is the most effective method to decrease the preterm birth rate in twin gestations. Whereas the increased use of these intense intervention programs should substan­tially decrease the preterm birth rate in high-risk pa­tients, our ability to minimize the overall preterm birth rate will continue to be limited as long as 40% to 60% of preterm births continue to occur in patients with no identifiable risk factors for preterm labor.5. 6

We gratefully acknowledge Elizabeth Wellman, RN, and Jane Dyson, RN, for their invaluable assistance with this study and Bruce Folck for computer programming.

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March 1991 Am J Obstet Gynecol

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15. Richter R. Evaluation of success in treatment of threat­ening premature labor by betamimetic drugs. AM J OB­STET GYNECOL 1977;127:482-6.

16. Newman RB, Gill PJ, Wittreich P, Katz M. Maternal per­ception of prelabor uterine activity. Obstet Gynecol 1986; 68:765-9.