Late Preterm Delivery in Women With Preterm Prelabour Rupture of Membranes

Objective: To estimate maternal and neonatal outcomes in women with preterm prelabour rupture of membranes (PPROM) who delivered at 34+0 to 36+6 weeks' gestation, particularly in those who had an obstetrically indicated delivery. Methods: We conducted a population-based study of late preterm singleton births complicated by PPROM, using data from the Nova Scotia Atlee Perinatal Database from 1988 to 2006. The study cohort was categorized by type of labour (spontaneous, induced, no labour), and each group's characteristics prior to delivery, and their outcomes were compared after accounting for potential confounding variables. Results: From a total population of 164 384 pregnancies, 2618 deliveries were identified as having PPROM. Among these, 2180 (83.3%) delivered between 34+0 and 36+6 weeks' gestation. Adjusted analyses showed no differences in risk between those women entering labour spontaneously (n = 1296) and those with obstetrically indicated delivery (labour induction or Caesarean section without labour, n = 698). Additional adjusted analyses evaluating only women with obstetrically indicated delivery showed that rates of chorioamnionitis (OR 0.27; 95% CI 0.08 to 0.93), composite perinatal morbidity/mortality (OR 0.39; 95% CI 0.25 to 0.62), neonatal depression at birth (OR 0.22; 95% CI 0.06 to 0.86), and respiratory distress syndrome (OR 0.17; 95% CI 0.06 to 0.47) were significantly lower in those delivering at 36 weeks (n = 458) than in those delivering at 34 to 35 weeks (n = 240). Conclusions: This large population-based study suggests that in pregnancies complicated by PPROM rates of adverse maternal and perinatal outcomes at 36 weeks' gestational age are at least comparable to those in pregnancies delivering at 34 to 35 weeks, and these rates may be further reduced by delivery after 36 completed weeks if spontaneous labour has not occurred.