Risk factors for postpartum hemorrhage after vaginal delivery of twins.

We examined vaginal deliveries of twins to identify factors most strongly associated with the increased risk of postpartum hemorrhage (estimated blood loss > or = 1,000 mL). We reviewed the obstetric records of all 171 twin vaginal deliveries at Japanese Red Cross Katsushika Maternity Hospital from January 2002 through August 2006. Of these deliveries, 41 (24%) were complicated by postopartum hemorrhage. Postpartum hemorrhage was significantly more likely in cases with gestational age > or = 39 weeks (odds ratio [OR], 3.47; 95% confidence interval [CI], 1.65-7.28), a combined birth weight of more than 5,500 g (OR, 2.53; 95% CI, 1.00-6.45), induction of labor (OR, 2.87; 95% CI, 1.38-5.98), oxytocin administration during labor (OR, 2.86; 95% CI, 1.27-6.48), or a duration of labor > or = 24 hours (OR, 2.55; 95% CI, 1.15-5.62). Postpartum hemorrhage is a frequent complication in twin pregnancies. Therefore, special attention should be given after birth to patients with induction of labor or intervened delivery especially at > or = 39 weeks gestation.