Duration of labor induction in nulliparous women with hypertensive disorders of pregnancy and maternal and neonatal outcomes.

OBJECTIVE

The objective of this study was to quantify the association between duration of labor induction in nulliparous women with hypertensive disorders of pregnancy and maternal and neonatal morbidity.

METHODS

This was a secondary analysis of a multicenter cohort study of 228,438 deliveries in 19 U.S. hospitals. The analysis included nulliparous women ≥18 years old with singleton gestation diagnosed with hypertensive disorders of pregnancy and undergoing induction of labor for that indication. Duration of labor induction, defined as time from admission to delivery, was examined by 4 h intervals from <12 h to ≥24 h in relation to maternal and neonatal composite outcomes. Maternal composite outcome included operative vaginal delivery, chorioamnionitis, blood transfusion, intensive care unit admission, placental abruption, 3rd or 4th degree perineal laceration, endometritis, postpartum hemorrhage, or venous thromboembolism. Neonatal composite outcome included neonatal intensive care unit (NICU) admission, respiratory distress syndrome, 5-minute Apgar score ≤7, seizure, infection, intrapartum meconium aspiration, intracranial hemorrhage, shoulder dystocia, and neonatal death. The trends in proportions of outcomes that occurred at different intervals were examined by Cochran-Armitage trend test. Relative risks were calculated with <12 h as the reference category and potential confounders adjusted by log-binomial or Poisson regression. Possible correlations within centers were taken into account using generalized estimating equations.

RESULTS

A total of 3,990 women met inclusion criteria. The median labor duration was 19.8 h (interquartile range 12.9 h-27.9h), with 849 (21.3%) lasting <12 h and 1,426 (35.7%) >24 h. The frequency of composite maternal outcome was not associated with labor duration; however, the rates of chorioamnionitis ( < .001) and postpartum hemorrhage ( < .001) increased as labor duration increased. The frequency of composite neonatal outcome was greater with increasing labor duration ( < .001). After multivariable adjustment, duration of labor induction was associated with increased risks of maternal composite outcome after 24 h (aRR 1.39, 95% CI 1.20-1.62) and neonatal composite outcome after 24 h (aRR 1.32, 95% CI 1.11-1.56).

CONCLUSIONS

In nulliparous women with hypertensive disorders of pregnancy, duration of labor induction was associated with increased risks for maternal and neonatal morbidity after 24 h.