846 Risk of stillbirth with history of prior cesarean deliveries

Abstract

The rate of US births delivered by cesarean has increased significantly, even for women considered to be at low risk for cesarean delivery (CD). The relationship between previous CD and subsequent stillbirth is unclear. We aim to examine the influence of prior CD, and increasing numbers of prior CDs, on the risk of subsequent stillbirth. Population-based retrospective cohort of all live births and stillbirths in the US 2014-2016 using CDC Vital Statics. Rates of stillbirth of multiparous woman with singleton gestations with prior history of vaginal deliveries (referent) were compared to a similar cohort with prior history of CD, and stratified by number of CDs (one, two, three and ≥ four). Rates of stillbirth were also compared at term, stratified by week of gestational age (GA) with comparison groups of one and ≥ two prior CDs (exposure groups consolidated due to small sample size in some comparisons). Multivariate logistic regression quantified the relationship between history of prior CDs and risk of stillbirth risk after adjustment for coexisting risk factors. Of the 7,614,326 singleton births in parous women, 77.8% had no prior CD and 22.2% had at least one prior CD. The rate of stillbirth was 4.27 per 1,000 births in women without prior CD vs 4.51 per 1000 births with prior CD, p<0.01. As the number of prior CDs increased, the rate of stillbirth increased linearly from 4.17 with one prior to 7.96 per 1,000 with ≥4 prior CDs, p < 0.01, r=0.93. The adjusted relative risk (aRR) of stillbirth was not significantly increased with one or two prior CDs, but increased with higher number of prior CDs, highest with four or more prior (aRR 1.38, 95% 1.17-1.63). At term, the aRR of stillbirth was significantly increased with two or more prior CDs, 38 weeks GA (aRR 1.40, 95% 1.16-1.69), 40 weeks GA (aRR 2.27, 95% 1.49-3.45). Stillbirth rates increase linearly with increasing number of prior CDs. Prior CD is associated with increased risk of stillbirth in women with three or more prior cesareans. Stillbirth risk is most pronounced at term, with >2-fold risk at 40 weeks.View Large Image Figure ViewerDownload Hi-res image Download (PPT)