The association between number of repeat cesarean deliveries and adverse outcomes among low-risk pregnancies

Objective To investigate maternal and neonatal adverse outcomes among low-risk pregnancies delivered at 37 weeks or more by repeat cesarean deliveries (CD). Methods A population-based, retrospective study using the US vital statistics data sets (2014-2018) evaluating low-risk pregnancies with a non-anomalous singleton non-laboring repeat CD from 37 to 41 weeks of pregnancy. Women with hypertensive disorders or diabetes were excluded. Primary outcome was composite maternal adverse outcome (CMAO). Secondary outcome was composite neonatal adverse outcome (CNAO). Multivariable Poisson regression models were used to estimate the association between number of repeat CD and outcomes (using adjusted relative risks [aRR] and 95% confidence interval [CI]). Results Of the 19 623 195 live births, 1 747 610 (8.9%) met the inclusion criteria and among them, 1 144 186 (65.5%) were to women who had one prior CD, 454 817 (26.0%) had two prior CD, 119 087 (6.8%) had three prior CD, and 29 520 (1.7%) had four or more prior CD. Compared with individuals with one prior CD, the risk of CMAO was higher in individuals with two (aRR 1.41, 95% CI 1.34-1.48), three (aRR 1.96, 95% CI 1.83-2.10), and four or more (aRR 2.98, 95% CI 2.69-3.29) prior CD. An increased risk of CNAO was also found with an increasing number of repeat CD. Conclusion Among women with low-risk pregnancies undergoing repeat CD, increasing number of prior CD was associated with a higher risk of adverse outcomes.