OTTAWA — Delivery more than 72 hours after preterm premature rupture of membranes was associated with a significantly reduced rate of neonatal morbidity in a retrospective review of more than 1,500 pregnancies at one Canadian center.
Induced or surgical delivery within 72 hours of preterm premature rupture of membranes (PPROM) was considered aggressive management, and delivery beyond 72 hours was considered conservative management.
“A policy of conservative management for advanced gestational age at PPROM will reduce severe infant morbidity at up to 32 weeks' gestation, and reduces moderate morbidity at up to 36 weeks,” Dr. Dan Nayot said at the annual clinical meeting of the Society of Obstetricians and Gynaecologists of Canada.
“Our data suggest taking a watch-and-wait approach through 36 weeks,” said Dr. Nayot, who performed this analysis while at the University of Western Ontario in London; he is now an ob.gyn. at the University of Toronto.
This finding, drawn from 10 years of data collected at a regional tertiary-care hospital in London, contrasts with what has become common practice at many centers in the United States, where aggressive induction of delivery is often used for PPROM after 32 weeks' gestation, noted Dr. Bryan Richardson, chairman of the department of ob.gyn. at the University of Western Ontario and senior researcher for this study.
“There has never been a randomized, controlled trial, but studies of data from the U.S. suggest there's no benefit from delaying delivery after 32 weeks' gestational age. A problem with those data is that they come from patient populations that are largely public institution-based, with patients from lower socioeconomic levels, and this may introduce possible confounders,” Dr. Richardson said in an interview. The London data come from what may be a more representative population mix, he said.
The study used data collected on all deliveries at St. Joseph's Health Care from 1996 to 2005. During that time there were 1,535 pregnancies where PPROM occurred after 24 weeks' and before 37 weeks' gestation and involved a singleton pregnancy with no major anomalies. These pregnancies accounted for 4.3% of all deliveries during this period. The analysis divided the PPROM deliveries into three subgroups: those that occurred during weeks 25–28, those during weeks 29–32, and those during weeks 33–36.
PPROM most often occurred at 33–36 weeks' gestational age and accounted for 72% of all episodes. PPROM was next most common during weeks 29–32 (19% of all episodes), and was least common during weeks 25–28 (10% of all episodes [total is 101% because of rounding]). Aggressive management was most frequent for near-term PPROM; 90% of all pregnancies with PPROM at 33–36 weeks were delivered within 72 hours. Aggressive delivery was used for 58% of PPROM deliveries during weeks 29–32, and in 33% of episodes during weeks 25–28.
Within both the near-term and preterm subgroups, earlier delivery was used more often for older gestational ages. In the 33- to 36-week group, the average age of the infants delivered within 72 hours was 35.2 weeks vs. 34.0 weeks in the conservative group. In the 29- to 32-week group, the average age of the infants who had aggressive delivery was 30.9 weeks vs. 30.5 weeks in those managed conservatively. In the pregnancies that had PPROM during weeks 25–28, the average age at delivery was 26.5 weeks in both subgroups.
Severe infant comorbidities included bronchopulmonary dysplasia, intraventricular hemorrhage grades 3 or 4, periventricular leukomalacia, necrotizing enterocolitis, retinopathy of prematurity grades 3 or 4, and perinatal death. Moderate comorbidities were respiratory distress syndrome, intraventricular hemorrhage grades 1 or 2, retinopathy of prematurity grades 1 or 2, and sepsis.
In pregnancies that had PPROM during 25–28 weeks or 29–32 weeks, aggressive management led to a significantly higher incidence of severe perinatal outcomes, Dr. Nayot said. (See graph.) In pregnancies that had PPROM at 29–32 weeks or 33–36 weeks, aggressive management significantly boosted the incidence of moderate perinatal comorbidities.
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