Obstetric history and the risk of placenta previa

Objective. To evaluate secular trends in the occurrence of placenta previa and whether placenta previa is associated with the outcome of previous pregnancies, cesarean section, and sociodemographic factors. Design. A cohort study based on the Medical Birth Registry of Norway. Placenta previa in the second pregnancy was investigated for associations with outcomes in the first pregnancy and sociodemographic factors. Results. In birth orders 1 and 2 the occurrence of placenta previa was 1.2 and 2.2 per 1000, respectively, with no secular trend. The occurrence increased with maternal age and was lowest in women aged 20-29 years. The recurrence rate was 23 per 1000 (adjusted odds ratio (OR) of recurrence=9.7). In women with prior delivery at ≤25 gestational weeks the risk of placenta previa was 6.7 per 1000 (adjusted OR=3.0). In women with prior placental abruption the risk was 5.8 per 1000 (OR=2.6). In women with prior perinatal death the risk was 4.4 per 1000 (adjusted OR=1.8). No independent relationship em...