Impact of labor induction on cesarean risk and maternal-fetal outcomes by gestational age in primiparas with a previous cesarean delivery: LUSTrial secondary analysis.

BACKGROUND

The optimal timing of delivery after a prior cesarean is debated. Induction of labor (IoL) may reduce the risk of repeat cesarean delivery (CD), but its safety remains unclear.

OBJECTIVE

To assess the risks of CD and maternal-neonatal morbidity associated with IoL vs expectant management (EM) from 38 weeks gestation onward in primiparous women with one prior CD.

STUDY

DESIGN

This secondary analysis of the randomized LUS Trial included primiparous women eligible for a trial of labor after cesarean (TOLAC) from 38 weeks to 0 days. CD rates and maternal-fetal morbidity were compared according to the intended management strategy: IoL or EM. Comparisons were made between women who underwent IoL at a specific gestational week and those who remained pregnant at the end of that week (EM group). Maternal and neonatal morbidities were assessed using composite criteria. Multivariable logistic regression models were adjusted for maternal characteristics (body mass index, diabetes, hypertensive disorders, suspected macrosomia) and hospital status.

RESULTS

Among the 2948 LUS Trial participants, 2267 primiparous women at ≥38 weeks of gestation with a prior CD were eligible, and 1778 (78.4%) underwent a TOLAC. Among them, 372 (20.9%) had an IoL and 1406 (79.1%) had a spontaneous labor. The CD rate was 44.2% (1002/2267) in the overall population. CD rates were similar in the IoL and EM groups week-by-week before 40 weeks 0 days. IoL between 40 weeks 0 days and 40 weeks 6 days was associated with a significant lower CD risk compared to EM beyond 41 weeks 0 days (adjusted odds ratio 0.66, 95% confidence interval 0.30-0.87). IoL at 39, 40, or 41 weeks was not associated with an increased composite maternal or neonatal morbidity.

CONCLUSION

In women with one prior CD, IoL at 40 weeks compared with EM beyond 41 weeks reduces the CD risk without increasing adverse maternal or neonatal outcomes. El resumen está disponible en Español al final del artículo.