A prior cesarean delivery is not associated with an increased risk of antepartum stillbirth in a subsequent pregnancy: Analysis of U.S. perinatal mortality data, 1995-1997

Abstract

Antepartum stillbirth (SB) is more common than deaths from prematurity and SIDS. Recent data suggests that a prior cesarean delivery may be a risk factor for SB in a next pregnancy (Smith et al. Lancet 2003; 362:1779). This study seeks to validate this observation in the U.S. maternity population. Of the 10,968,708 singleton gestations >20 weeks recorded in the CDC Perinatal Mortality Database (1995-1997), 88,812 (0.8%) were excluded due to incomplete records and 6,819,367 (62.2%) due to preexisting medical conditions, congenital anomalies, or no prior delivery. The risk of SB in the remaining 4,060,529 pregnancies was calculated as a function of maternal age, ethnicity (non-Hispanic white vs non-Hispanic black), number of prenatal visits, and route of delivery grouped as ‘prior cesarean’ (index pregnancy delivered by VBAC or repeat cesarean) or ‘no prior cesarean’ (normal vaginal delivery or primary cesarean). Logistic regression and chi-square tests were used for data analysis. The overall incidence of SB was 118 per 100,000 pregnancies (4805/4,060,529), but was higher in black compared with white populations: 200 (1172/584,898) vs 92 (2299/2,491,983) per 100,000 pregnancies, respectively (P < .0001). Maternal age and number of prenatal visit did not correlate with risk of SB. Overall, risk of SB was significantly decreased in women with prior cesarean delivery compared with no prior cesarean delivery: 78 (510/653,741) vs 126 (4295/3,406,788) per 100,000 pregnancies (RR, 0.62; 95% CI, 0.56-0.68; P < .001). This was evident in both white and black populations: 68 (281/415,632) vs 97 (2018/2,076,351) per 100,000 pregnancies (RR, 0.69; 95% CI, 0.61-0.79; P < .001) and 125 (113/90,449) vs 214 (1059/495,449) per 100,000 pregnancies (RR, 0.58; 95% CI, 0.48-0.71; P < .001), respectively. These data do not support recent studies suggesting that prior cesarean delivery is associated with an increased risk of SB > 20 weeks in a subsequent pregnancy. Indeed, cesarean delivery may be protective of subsequent SB in the U.S. population.