Placental abruption and premature rupture of membranes

Objective. To assess whether premature rupture of membranes (PROM) is associated with placental abruption. Design. Population-based study. Setting. Data were extracted from the Medical Birth Registry of Norway. Population. All women with PROM(18 889 cases), including 3 077 cases of preterm premature rupture of membranes (p-PROM), among a total of 355 416 singleton births in Norway during 1999-2005 with gestational age 17-44 weeks. Methods. Logistic regression was used to assess whether placental abruption was associated with PROM in preterm and term births. Main Outcome Measures. Placental abruption. Results. The occurrence of placental abruption in p-PROM was higher than in the total study population, 11.0 per 1 000 (34 of 3 077) vs. 4.2 per 1 000 (1 495 of 355 416; adjusted odds ratio 2.6, 95% confidence interval 1.8-3.7). Restricting the analyses to preterm births, the occurrence of placental abruption was less in p-PROM (11.0 per 1 000) than in births without p-PROM (36.1 per 1 000; adjusted odds ratio 0.3, 95% confidence interval 0.2-0.4). In term births, no statistically significant association was observed. Conclusions. The findings suggest that in p-PROM the risk of placental abruption is not higher than in other preterm births; rather the opposite. However, comparing the risks in p-PROM and the total gestational age range, the present study confirmed results reported in previous studies of a higher risk of placental abruption in p-PROM than in the total birth population.