Institute of Clinical Medicine, University of Bergen Medical Birth Registry of Norway, Norwegian Institute of Public Health Department of Obstetrics and Gynecology, Haukeland University Hospital University Research Bergen, Department of Health, University of Bergen Locus for Registry Based Epidemiology, Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway.
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 17-44weeks. 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.