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ORIGINAL RESEARCH |
From the Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas.
Address reprint requests to: James M. Alexander, MD, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235-9032, E-mail: jalexa{at}mednet.swmed.edu
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Abstract |
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Methods: This was a retrospective study of 278 singleton, live-born infants who weighed 750–1500 g and were delivered because of severe preeclampsia between 1988 and 1997. Outcomes of infants delivered by cesarean without labor were compared with those of infants exposed to labor induction. Statistical analysis was performed using Student t test, Mann-Whitney U test, 
2 analysis, and Fisher exact test, where appropriate. Multiple logistic regression analysis was used to adjust for outcomes of interest.
Results: One hundred forty-five (52%) of the 278 women with severe preeclampsia who delivered infants weighing between 750 and 1500 g had labor induced and 133 (48%) delivered by cesarean without labor. Vaginal delivery was accomplished by 50 (34%) women in the induced group. Apgar scores of 3 or less at 5 minutes were more likely in the induced-labor group (6 versus 2%, P = .04), but other neonatal outcomes, including respiratory distress syndrome, grade 3 or 4 intraventricular hemorrhage, sepsis, seizures, and neonatal death, were similar in the two groups. Adjustment for birth weight and gestational age did not affect those results. Analysis of data from the induced-labor group did not reveal an effect by route of delivery on neonatal outcome.
Conclusion: Induction of labor in cases of severe preeclampsia is not harmful to very low birth weight infants.
Severe preeclampsia is an indication for preterm delivery in the United States.1 Once severe preeclampsia is diagnosed, the obstetric propensity is for prompt delivery. Induced labor to effect vaginal delivery was considered to be in the best interest of the mother.2 Several concerns, including an unfavorable cervical condition precluding successful induction of labor, a perceived sense of urgency because of the severity of preeclampsia, and the need to coordinate neonatal intensive care, have led some to advocate cesarean delivery.
In addition to the perception that induction of labor might not be successful, it has been reported that labor might be harmful to preterm fetuses. Bejar and colleagues3 reported that preterm infants frequently had germinal intraventricular hemorrhage, prompting the idea that cesarean delivery prevented trauma from labor and might reduce those complications. However other studies of the effects of labor on the fetus with cephalic presentation supported the concept that avoiding labor conferred no advantage to the premature fetus.3–8 For example, Malloy and colleagues8 concluded that the cesarean delivery rates for very low birth weight (VLBW) infants doubled between 1980 and 1984 in Missouri, without benefits to the infants.
In the last decade, as before,2 the obstetric practice at our hospital has been to induce labor when severe preeclampsia warranted delivery of preterm infants. The purpose of this study was to assess the success and safety of our practice of labor induction when preterm delivery was indicated because of severe preeclampsia.
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Materials and Methods |
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In this investigation, data from women whose infants were delivered because of severe preeclampsia were analyzed. Outcomes of infants exposed to labor induction were compared with those of infants delivered by cesarean without labor. We limited the analysis to infants with birth weights between 750 and 1500 g because intrapartum management of smaller fetuses might have been influenced by concerns about viability. Very low birth weight infants with malformations and those from multiple gestations also were excluded.
Severe preeclampsia was diagnosed when blood pressure was at least 160/110 mmHg or at least 140/90 and other features of severe preeclampsia were present, including worsening proteinuria (2+ or greater), thrombocytopenia (platelet count less than 100,000/mm3), elevated liver transaminase levels, and symptoms of severe disease such as visual disturbances, epigastric pain, or unrelenting headaches. Women with severe preeclampsia received intramuscular magnesium sulfate for seizure prophylaxis and intravenous (IV) hydralazine in 5- to 15-mg boluses for severe hypertension. Glucocorticoids were not given for fetal lung maturation to women with preeclampsia.
Women with severe preeclampsia had labor induced with continuous IV oxytocin infusion. Contraindications included fetal malposition, placenta previa, active genital herpes, and previous uterine scar. Before November 1, 1990, labor was induced with low-dose oxytocin, starting with 1 mU/minute, followed by increases of 1 mU/minute at 20-minute intervals until 8 mU/minute, then by 2-mU/minute increases up to 20 mU/minute.9 After November 1, 1990, a high-dose regimen of oxytocin was instituted, consisting of a starting dose of 6 mU/minute, followed by increases of 6 mU/minute at 20-minute intervals up to 42 mU/minute. On May 1, 1992, the interval between dose changes was increased to 40 minutes.9 The continuous infusion rate was halved to 3 mU/minute in cases of uterine hyperstimulation. Recurrent hyperstimulation was managed with oxytocin in increasing increments of 1 mU/minute. After active labor began (ie, when cervical dilation was 4 cm or greater), dystocia was not diagnosed until uterine activity of 200–250 Montevideo units had occurred for 2–4 hours. Dilation rates of 1–2 cm/hour were considered evidence of labor progress.
Statistical analyses were performed using Student t test for continuous variables, 2, and Fisher exact or logistic regression for categorical data. All data were analyzed using SAS statistical software (SAS Institute, Cary, NC). P < .05 was considered significant. All tests of significance were two-sided.
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Results |
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). The majority of women in each study group had proteinuria.
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. Vaginal delivery occurred in 50 (34%) of the 140 women in whom labor was induced. The remaining 228 women, 82% of the total cohort, had cesarean deliveries. Indications for cesarean delivery differed between the two study groups. Mal-presentation and prior cesarean delivery were the leading indications for cesarean delivery without labor. Severe preeclampsia was the single indication for cesarean delivery in 22 (17%) of the women in whom labor was not induced. Leading indications for cesarean delivery in women with induced labor were nonreassuring fetal heart rate and failed induction (35 and 23%, respectively).
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). The only infant morbidity that was significantly increased with induced labor was 5-minute Apgar scores of 3 or less (6 versus 2%, P = .04). Logistic regression analysis, adjusting for birth weight and gestational age, showed that neonatal outcomes assessed with univariate analysis (Table 3) remained independent of labor induction. The odds ratios (95% confidence intervals) were as follows: Apgar score of 3 or less at 5 minutes, 6.1 (1.1, 32.2); umbilical artery (UA) blood pH no more than 7.0, 0.61 (0.06, 6.4); respiratory distress, 1.5 (0.84, 2.7); sepsis, 5.4 (0.54, 52.6); intraventricular hemorrhage, grade 3 or 4, 3.9 (0.99, 15.6); and seizures, 3.7 (0.27, 5.0).
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). Although UA blood pH values of less than 7.0 were significantly more frequent in infants delivered vaginally than by cesarean after failed induction (0 versus 4%, P = .05), there were no differences in neonatal deaths or other indices of morbidity.
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Discussion |
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A MEDLINE search, inclusive of the years 1966–1998 and using the search words "very low birth weight," "preeclampsia," and "induction of labor," yielded no reports that specifically addressed the efficacy and safety of labor induction because of severe preeclampsia in women who delivered VLBW infants. Such pregnancies are difficult to study because it is uncommon for women to need delivery at that early gestational age. Between 1988 and 1997, the average number of births at our hospital each year was approximately 14,000, and there were only 27 deliveries per year of VLBW infants because of severe preeclampsia. The ideal way to study this issue would be to randomize women to a route of delivery. This likely would be impossible, because of the large number of subjects required and the inordinate amount of time the study would take. For example, we observed a statistically insignificant (P = .09) increase in intraventricular hemorrhage from 2 to 7% in women who delivered without labor compared with those in whom labor was induced. That difference would become statistically significant if our total cohort had included approximately 1300 women. It would take approximately 40 years for such a data set to accumulate at our hospital. Thus, the effects of labor induction on neonatal outcome will likely remain unknown.
Studying the effects of labor and routes of delivery on preterm fetuses not only requires large data sets, but also requires controlling for several potentially confounding therapies that have been reported to affect neonatal neurologic morbidity. Ment and colleagues10 reported that antenatal steroids given for fetal lung maturation protect against intraventricular hemorrhage. Nelson and Grether11 suggested that magnesium sulfate protects preterm infants against cerebral palsy. Murphy and colleagues12 concluded that preeclampsia itself, rather than magnesium sulfate, was neuroprotective against cerebral palsy because magnesium sulfate was not used for management of preeclampsia in their population. In our study, none of the fetuses were exposed to antenatal corticosteroids, and all were delivered by women given magnesium sulfate to prevent eclampsia. Given the potential of corticosteroids and magnesium sulfate to modify neurologic outcomes, we believe that the homogeneity of our cohort (ie, the fact that all subjects had no corticosteroid therapy and there was uniform administration of magnesium sulfate) was conducive to measuring effects, or lack thereof, of labor induction. Thus, two potential confounding variables were minimized.
We were disappointed that despite 10 years of data collection and relatively uniform management practices, we were unable to resolve definitively whether labor induction is harmful or beneficial to VLBW infants. We believe that answering this question is not feasible because of the relative infrequency of severe preeclampsia leading to delivery of VLBW infants and the many potential confounding variables that affect morbidity in very immature infants. We will continue to use labor induction as our usual contemporary practice.
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Footnotes |
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Received June 18, 1998. Received in revised form September 28, 1998. Accepted October 15, 1998.
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References |
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2. Cunningham FG, MacDonald PC, Gant NF, Leveno KJ, Gilstrap LC III, Hankins GDV, et al. Williams obstetrics. 20th ed. Stamford, Connecticut: Appleton & Lange, 1997.
3. Bejar R, Curbelo V, Coen RW, Leopold G, James H, Gluck L. Diagnosis and follow-up of intraventricular and intracerebral hemorrhages by ultrasound studies of infant’s brain through the fontanelles and sutures. Pediatrics 1980;66:661–73.
4. Strauss A, Kirz D, Modanlou HD, Freeman RK. Perinatal events and intraventricular/subependymal hemorrhage in the very low-birth weight infant. Am J Obstet Gynecol 1985;151:1022–7.[Medline]
5. Welch RA, Bottoms SF. Reconsideration of head compression and intraventricular hemorrhage in the vertex very-low-birth-weight fetus. Obstet Gynecol 1986;68:29–34.[Medline]
6. Newton ER, Haering WA, Kennedy JL Jr, Herschel M, Cetrulo CL, Feingold M. Effect of mode of delivery on morbidity and mortality of infants at early gestational age. Obstet Gynecol 1986;67:507–11.
7. Morales WJ, O’Brien WF, Knuppel RA, Gaylord S, Hayes P. The effect of mode of delivery on the risk of intraventricular hemorrhage in nondiscordant twin gestations under 1500 g. Obstet Gynecol 1989;73:107–10.
8. Malloy MH, Rhoads GG, Schramm W, Land G. Increasing cesarean section rates in very-low-birthweight infants. Effects on outcome. JAMA 1989;262:1475–8.[Abstract]
9. Satin AJ, Leveno KJ, Sherman ML, Brewster DS, Cunningham FG. High- versus low-dose oxytocin for labor stimulation. Obstet Gynecol 1992;80:111–6.
10. Ment LR, Oh W, Ehrenkranz RA, Philip AGS, Duncan CC, Makuch RW. Antenatal steroids, delivery mode, and intraventricular hemorrhage in preterm infants. Am J Obstet Gynecol 1995;172:795–800.[Medline]
11. Nelson KB, Grether JK. Can magnesium sulfate reduce the risk of cerebral palsy in very low birthweight infants? Pediatrics 1995;95: 263–9.
12. Murphy DI, Sellers S, MacKenzie IZ, Yudkin PL, Johnson AM. Case-control study of antenatal and intrapartum risk factors for cerebral palsy in very preterm singleton babies. Lancet 1995;346: 1449–54.[Medline]
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