Risk of perinatal death associated with labor after previous cesarean delivery in uncomplicated term pregnancies.

CONTEXT Trial of labor after previous cesarean delivery is associated with increased risk of uterine rupture. However, no reliable data exist on the effect of a trial of labor on the risk of perinatal death in otherwise uncomplicated term pregnancies. OBJECTIVE To determine the risk of intrapartum stillbirth or neonatal death not related to congenital abnormality among women with uncomplicated term pregnancies who had a trial of labor after previous cesarean delivery, compared with women having a planned repeat cesarean delivery, and multiparous and nulliparous women at term not delivered by planned cesarean method. DESIGN AND SETTING Population-based, retrospective cohort study of data from the linked Scottish Morbidity Record and Stillbirth and Neonatal Death Enquiry encompassing births in Scotland between January 1, 1992, and December 31, 1997. POPULATION A total of 313 238 singleton births between 37 and 43 weeks' gestational age in which the fetus was in a cephalic presentation. MAIN OUTCOME MEASURE Delivery-related perinatal death, defined as intrapartum stillbirth or neonatal death unrelated to congenital anomaly, compared among the 4 groups. RESULTS Among women who had a trial of labor following previous cesarean delivery (n = 15 515), the overall rate of delivery-related perinatal death was 12.9 (95% confidence interval [CI], 7.9-19.9) per 10 000 women. This was approximately 11 times greater (odds ratio [OR], 11.6; 95% CI, 1.6-86.7) than the risk associated with planned repeat cesarean delivery (n = 9014), more than twice (OR, 2.2; 95% CI, 1.3-3.5) the risk associated with other multiparous women in labor (n = 151 549), and similar to the risk among nulliparous women in labor (n = 137 160; OR, 1.3; 95% CI, 0.8-2.1). The associations were not explained by differences in maternal height, smoking status, socioeconomic status, age, fetal growth, or week of gestation at delivery. Among women having a trial of labor, the rate of death due to mechanical causes, including uterine rupture, was 4.5 (95% CI, 1.8-9.3) per 10 000 women. This was more than 8 times greater than other multiparous women (OR, 8.5; 95% CI, 3.2-22.3) and nulliparous women (OR, 8.8; 95% CI, 3.2-24.2). CONCLUSIONS The absolute risk of perinatal death associated with trial of labor following previous cesarean delivery is low. However, in our study, the risk was significantly higher than that associated with planned repeat cesarean delivery, and there was a marked excess of deaths due to uterine rupture compared with other women in labor.