Mark J Bergeron, MD; Yasuko Yamamura, MD; Kirk D Ramin, MD, and Catherine M Bendel, MD
Date of Defense:
Background: Considerable variation exists in the obstetric management of maternal preterm premature rupture of membranes (PPROM) based on perceptions of neonatal morbidity risks. Lack of consensus exists regarding optimal time to facilitate delivery at later gestational ages (GA) for pregnancies complicated by PPROM at 32-33 weeks. This is a particularly important group, from a public health perspective, because nearly 13% of preterm births occur in this gestational age range, representing a substantial health care burden.
Objective: Assess the quantitative contribution of PPROM to morbidity for preterm infants born between 32 0/7 weeks and 33 6/7 weeks compared to preterm labor (PTL). Morbidity differences between 32 and 33 weeks GA within the two groups were also sought.
Design/Methods: A retrospective observational study using a comprehensive neonatal database including infants delivered between 32 0/7 and 33 6/7 weeks gestation from 2005-2006 at the University of Minnesota Medical Center, Fairview. Infants born following either spontaneous PTL or PPROM were included. PTL was defined as spontaneous uterine contractions resulting in cervical change. PPROM was defined as spontaneous rupture of membranes prior to the onset of labor at less than 37 completed weeks. Outborn infants and cases due to iatrogenic preterm delivery, multiple gestations, or congenital anomalies were excluded. Primary end point: hospital discharge; primary outcomes: length of stay (LOS) and incidence of respiratory distress syndrome (RDS). Secondary measures: incidence of intraventricular hemorrhage (IVH), necrotizing enterocolitis (NEC) and sepsis. Chi-Square, Student’s t-test and Fishers exact tests were utilized for statistical analysis.
Results: 49 cases met inclusion criteria (PPROM: N=36; PTL: N=13). There was no difference between the two groups in maternal age, race/ethnicity, antenatal betamethasone status, GBS colonization, Apgar scores or birth weight. Delivery by cesarean section was approximately three times as common in the PTL group (61.6%, N=8 vs. 19.5%, N=7; p=.02). There was no difference in the mean LOS (PTL 21.8 ± 6 days vs. PPROM 20.4 ± 9.5 days, p=0.61), RDS (PTL 23.1%, N=3 vs. PPROM 27.8%, N=10; p=0.74), or the incidence of IVH (PTL 23.1%, N=3 vs. PPROM 11.1%, N=4; p=0.34). Only two cases of NEC were reported and no cases of sepsis were diagnosed. When stratified by gestational age, mean LOS was longer for infants born at 32 weeks vs. 33 weeks in both groups (PTL: 26.7 ± 4.5 days vs. 17.7 ± 3.5 days, p<0.001; PPROM 26.9 ± 9.6 days vs. 15.2 ± 5.5 days, p<0.001).
Conclusions: Delaying delivery until later gestational age, when feasible, may translate into shorter LOS without increased neonatal morbidity and lower health care costs. Future prospective studies in this area are needed, and should include measurement of long-term neurodevelopmental outcomes.