Commentary and Review by:
Geffrey H. Klein, MD
OBGYN.net Advisory Board Chairman
Title: Premature rupture of membranes at 34 to 37 weeks' gestation: Aggressive versus conservative management
Reference: Am J Obstet Gynecol 1998;178:126-30
Authors: Naef III RW, Allbert JR, Ross EL,Weber BM, Martin RW, Morrison JC
Institutions: Depts of Obstetrics and Gynecology, University of Mississippi Medical Center, Carolinas Medical Center, and Keesler US Air Force Medical Center.
Study Design: Randomized Controlled Trial
Rating:Abstract:
Objective: Our purpose was to compare induction of labor with preterm rupture of membranes between 34 and 37 weeks' gestation with expectant management.
Study Design: In this prospective investigation 120 gravid women at „34 weeks 0 days and <36 weeks 6 days of gestation were randomized to receive oxytocin induction (n=57) or observation (n=63).
Results: Estimated gestational age at rupture of membranes (34.3 ± 1.4 weeks vs. 34.5 ± 1.4 weeks) and ultrasonographically estimated fetal weight (2230 ± 321 gm vs 2297 ± 365 gm) were equivalent between groups (not significant). Chorioamnionitis occurred more often (16% vs 2%, p=0.007), and maternal hospital stay (5.2±6.8 days vs 2.6±1.6 days, p= 0.006) was significantly longer in the control group. Neonatal sepsis was also more common in the observation group (n=3) than among induction patients (n=0), but the difference was not statistically sigificant.
Conclusion: Aggressive management of preterm premature rupture of the membranes at „34 weeks 0 days of gestation by induction of labor is safe for the infant in our population and avoids maternal-neonatal infectious complications.Commentary:
The issue of whether to expectantly or actively manage patients who present with premature rupture of membranes is controversial. Clinicians must weigh the risks of prematurity and potentially increased cesarean rates against the risks of maternal or fetal infections, fetal distress, and in utero fetal demise. A secondary concern is that this condition be managed in a cost-effective manner. Most would agree that that prior to 32 weeks, in the absence of fetal compromise or chorioamnionitis, expectant management is the wisest course. At term, there is data to suggest that induction reduces the risk of infection without increasing the risk of cesarean section. The question of the appropriate course of action at gestational ages in between has not been adequately answered. Naef, et al have designed a randomized controlled trial to provide data that may help answer this question.
This investigation was a randomized controlled trial. It was conducted from 1992 to 1994 at the University of Mississippi Medical Center in Jackson, Mississippi. Eligible participants were gravidas with documented rupture of membranes from 34 to 36 6/7 weeks gesatation by good dating criteria or with a sonographically estimated fetal weight between 1800 and 2500 g. Exclusion criteria included non-cephalic presentation, fetal distress, labor on admission, and medical/obstetrical complications including chorioamnionitis, hypertension, diabetes, genital herpes, placenta previa, meconium-stained fluid, and severe fetal anomalies. The patients were randomly assigned to one of two arms of the study, active treatment or expectant management. Those expectantly managed were admitted to the hospital, placed on bedrest, and given intravenous ampicillin for beta streptococcus prophylaxis. Tocolysis was not used and patients were allowed to deliver if active labor ensued. Other indications for delivery included chorioamnionitis or non-reassuring fetal heart rate tracing. Actively managed patients were started on pitocin by intravenous infusion. All patients who developed chorioamnionitis were treated with intravenous ampicillin and gentamicin. Neonatal outcome variables included culture proven sepsis, respiratory distress syndrome, bronchopulmonary dysplasia, patent ductus arteriosus, intraventricular hemorrhage, and necrotizing enterocolitis.
There were one-hundred twenty women enrolled in the trial. Fifty-seven were randomized to active treatment and sixty-three to expectant management. The groups did not differ in demographic or clinical characteristics. Greater than seventy-five percent were African American, the average age was twenty-two to twenty-three years old, approximately half were primigravidas, the average estimated gestational age was thirty-four weeks, and the estimated fetal weights on admission were 2200-2300 g. The overall incidence of chorioamnioitis was eight times higher in the expectant management arm (16% versus 2%). Expectantly managed patients had hospitalizations that averaged almost three days longer than actively managed patients (5.2 days versus 2.6 days). The incidence of cesarean delivery was similar for both groups, seven percent in the actively treated group versus five percent in the expectantly managed group. The authors note that no abdominal delivery was performed for the indication of failed induction, but rather for non-reassuring fetal status or arrest of labor. There were no statistically significant differences in any of the neonatal outcome variables. NICU admissions were approximately one in five. There were low rates of respiratory distress syndrome, five percent, and mechanical ventilation, three to five percent. There were no cases of intraventricular hemorrhage, patent ductus arteriosus, bronchopulmonary dysplasia, neonatal death, or stillbirth. There were three infants who developed sepsis in the expectant management group versus none in the actively treated group, but this was not statistically significant.
The authors concluded that actively managing patients with preterm premature rupture of membranes at 34 to 36 6/7 weeks resulted in less infectious morbidity and less hospital costs when compared with expectant mangement. Those expectantly managed were not spared any neonatal complications or cesarean deliveries due to failed induction. The authors state that "Patients with preterm premature rupture of membranes at 34 to 37 weeks' gestation should be considered as candidates for induction of labor."
The study of Naef, etal is an interesting one in its results. There are some aspects of the paper that may limit its universal applicability. The authors do acknowledge that the rates of respiratory distress syndrome in this study were very low when compared with Robertson, etal (1). Robertson, etal demonstrated a rate of respiratory distress syndrome of 13% at 34 weeks vs. 5% for both arms in the study of Naef, etal. The authors offer the study population as an explanation. Whereas, the patients in the study of Robertson, etal are mainly caucasian and affluent, the patients in the study of Naef, etal are mainly indigent and African American. An alternate/additive explanation might be one of the selection criteria, namely the inclusion of patients with birth weights estimated by ultrasound to be between 1800 and 2500 g. If the authors were unable to include patient's based on reliable dating criteria, it might be inferred that some were included with more mature fetuses that were simply small for gestational age. This would most certainly result in lower rates of complications of prematurity overall. Thus, the power of the study would decline and it would be difficult to demonstrate improvement in neonatal complications in the expectantly managed group. It would have been helpful for the authors to describe the numbers of patients included based on ultrasound estimated fetal weight and their distribution into each arm of the study. The authors exclusion criteria resulted in a low rates of abdominal delivery in both arms. They did concede this fact and stated that inclusion of patients with abnormal fetal heart rate tracing or meconium would have increased the rate of cesarean deliveries. In addition, they excluded non-vertex presentations as well. Prior to term, the proportion of fetus in the non-vertex presentation is higher than at term. Inclusion of these patients, and distributing them equally, would have certainly increased the total cesarean rate for both arms but should not have altered the fact that inducing labor added no extra risk of abdominal delivery. A more notable exclusion criteria might have accounted for the overall low incidence of neonatal complications. Namely, the exclusion of diabetic patients who have previously been noted to have delayed pulmonary maturity. Inclusion of diabetic patients might have resulted in a measurable improvement in neonatal complication rates with expectant management. It would have been helpful had the authors noted the number of patients excluded during the study period and for what indication.
This study did not attempt to incorporate documentation of pulmonary maturity. Two similar studies required documented pulmonary maturity as a selection criteria. Spinnato, etal (2) identified 99 patients, similar in demographics to the study of Naef, etal, with PPROM prior to 36 weeks and documented pulmonary maturity. Fifty-two were in labor and delivered. The remainder were randomized to delivery (N=26) or expectant management (N=21). There were no failed inductions and complications of prematurity were not statistically different. Mercer, etal (3) studied 93 women with PPROM at 32 to 36 6/7 weeks' gestation and documented pulmonary maturity. Patients were randomized to either induction of labor (N=46) or expectant management (N=47). The average gestational age of 34 weeks was comparable to the study of Naef, etal. They found that the expectantly managed group had prolonged maternal and fetal hospitalizations, an increased risk of chorioamnionitis, and more fetal heart rate abnormalities all without a reduction in neonatal sepsis. The issue of testing for pulmonary maturity prior to induction has also been studied. Stedman, etal (4) studied the vaginal pool of amniotic fluid in patients with PPROM for the presence of PG. Respiratory distress syndome occurred in none of the 28 PG positive patients and in four of the 19 PG negative patients. This was again later studied by Cotton, etal (5). Transabdominal amniocentesis in 42 patients with PPROM revealed over 60% with a mature L:S ratio. Compared vaginal pool amniotic fluid showed similar L:S ratios. Gram stain and culture of the transabdominal fluid predicted 7 of 7 patients who would go on to develop chorioamnionitis or endometritis. The authors reviewed the literature and concluded that prior to 32 weeks amniocentesis should not be performed due to the morbidity of prematurity regardless of pulmonary maturity status. In patients with gestations between 32 and 34 weeks gestation, amniocentesis can help guide the decision for delivery. In patients with gestational ages 34 weeks or greater, delivery should be considered without amniocentesis in all but those patients in whom delayed pulmonary maturity is suspected.
This study is another piece to the puzzle of management of patients from 32 to <37 weeks gestation with rupture of membranes. The best way to answer the question of management is to design a larger randomized multicenter study. The study should be designed in such a way as to include a more diverse racial and ethnic population. It should seek to stratify risks for either management scheme based on demographics, gestational age incriments of one week, and amniocentesis results for the presence of pulmonary maturity or indicators of infection.
Related Articles:
- Robertson PA. Sniderman SH. Laros RK Jr. Cowan R. Heilbron D. Goldenberg RL. Iams JD. Creasy RK. Neonatal morbidity according to gestational age and birth weight from five tertiary care centers in the United States, 1983 through 1986. Am J Obstet Gynecol 166(6 Pt 1):1629-45.
- Spinnato JA. Shaver DC. Bray EM. Lipshitz J. Preterm premature rupture of the membranes with fetal pulmonary maturity present: a prospective study. Obstetrics & Gynecology. 69(2):196-201, 1987 Feb.
- Mercer BM. Crocker LG. Boe NM. Sibai BM Induction versus expectant management in premature rupture of the membranes with mature amniotic fluid at 32 to 36 weeks: a randomized trial. American Journal of Obstetrics & Gynecology. 169(4):775-82, 1993 Oct.
- Stedman CM. Crawford S. Staten E. Cherny WB. Management of preterm premature rupture of membranes: assessing amniotic fluid in the vagina for phosphatidylglycerol. Am J Obstet Gynecol. 140(1):34-8, 1981 May 1.
- Cotton DB. Hill LM. Strassner HT. Platt LD. Ledger WJ. Use of amniocentesis in preterm gestation with ruptured membranes. Obstet Gynecol. 63(1):38-43, 1984 Jan.
