Abstract
Background
Worsening neonatal outcomes over time among planned vaginal births following a previous cesarean were reported in Canada; what drove the change remained unclear.
Objective
We aimed to describe time trends in severe maternal and perinatal–neonatal morbidity associated with a planned vaginal birth vs a repeat cesarean after a previous cesarean delivery and identify risk factors associated with the trends.
Study Design
This population-based cohort study included all singleton births ≥37 weeks’ gestation from Nova Scotia, Canada, April 1, 2003 to March 31, 2021 with 1 previous cesarean and without trial of labor contraindications. Primary outcomes were severe maternal morbidity and severe perinatal–neonatal morbidity. Adjusted risk ratios and 95% confidence intervals were estimated using log-binomial regression, accounting for confounding using inverse probability weighting.
Results
Among 12,681 births (4% aged ≥40 years), 5138 (40.5%) had a planned vaginal birth. Among those with a planned vaginal birth vs a repeat cesarean, severe maternal morbidity increased over time, from 5.9 vs 5.0 per 1000 deliveries in 2003–2008 (adjusted risk ratio, 1.13; 95% confidence interval, 0.46–2.8) to 17.3 vs 4.3 per 1000 deliveries in 2015–2021 (adjusted risk ratio, 3.4; 95% confidence interval, 1.38–8.2). In addition, severe perinatal–neonatal morbidity increased over time from 10.6 vs 10.0 per 1000 deliveries in 2003–2008 (adjusted risk ratio, 1.18; 95% confidence interval, 0.60–2.3) to 25.1 vs 17.2 per 1000 deliveries in 2015–2021 (adjusted risk ratio, 1.56, 95% confidence interval, 0.98–2.5). Any oxytocin induction or augmentation of labor increased from 12.1% in 2003–2008 to 37.9% in 2015–2021; its use was strongly associated with severe maternal morbidities in 2015–2021.
Conclusion
Planned vaginal birth vs a repeat cesarean after a previous cesarean delivery was more strongly associated with severe maternal and perinatal–neonatal morbidity in later years. Oxytocin induction and augmentation increased markedly in this population and could not be ruled out as a factor associated with worsening outcomes.