Risk of Perinatal Death Associated With Labor After Previous Cesarean Delivery in Uncomplicated Term Pregnancies

Abstract

Although a trial of labor after a past cesarean delivery is known to carry an increased risk of uterine rupture, there is no reliable information on whether it also increases the risk of perinatal death in otherwise uncomplicated term pregnancies. This question was addressed in a retrospective, population-based cohort study comprising 313,238 singleton births at 37 to 43 weeks' gestation where the fetus was in a cephalic presentation. At 12.9 per 10,000 women, the rate of perinatal death was highest for women having a trial of labor. The odds ratio (OR), compared with women having a planned repeat cesarean delivery, was 11.6. The risk of death from a trial of labor was similar when compared with that for nulliparous women in labor, but it was more than twice that of other multiparous women in labor (OR, 2.2). More than 90% of all delivery-related perinatal deaths among women with a previous cesarean delivery were attributable to the increased risk associated with a trial of labor. Adjusting for maternal age, smoking status, height, gestational age at birth, and birth weight strengthened the association between a trial of labor and perinatal death compared with elective repeat cesarean delivery. Similar results were obtained when only births at or after 40 weeks' gestation were analyzed. Compared with other multiparas, those having a trial of labor were more than 8-fold likelier to have a perinatal death due to a mechanical cause and nearly 3-fold likelier to have a perinatal death due to intrapartum anoxia. Although the absolute risk of perinatal death in women with a past cesarean delivery who undergo a trial of labor is low, the risk in the present study was higher than that of planned repeat cesarean delivery.