Comparing the second stage in induced and spontaneous labor.

OBJECTIVE

To compare the duration and complications of the second stage of labor between women in induced and spontaneous labor.

METHODS

This was a retrospective cohort study of women with singleton term gestations who reached full dilation at a single institution from 2001 through 2009. Second-stage duration, mode of delivery, and complication rates were compared between women in induced and spontaneous labor using survival analysis, univariable analysis, and multivariable analyses to control for potential confounders.

RESULTS

We identified 14,727 women who reached the second stage; 3,139 (21.3%) were induced and 11,588 (78.7%) were in spontaneous labor. After adjusting for confounders (maternal age, body mass index, epidural use, gestational age, midwifery care, health center care, year of delivery), there was no difference in length of the second stage or risk of a prolonged second stage between women in induced and spontaneous labor. In both groups, risk of complications increased with duration of the second stage, including chorioamnionitis, postpartum hemorrhage, third- or fourth-degree laceration, operative vaginal delivery, and 5-minute Apgar score less than 7. Among nulliparas who reached full dilation, our data suggested an increased odds of cesarean (10.9% compared with 7.2%, adjusted odds ratio [OR]1.32, 95% confidence interval [CI] 1.01-1.71) and postpartum hemorrhage (4.2% compared with 2.0%, adjusted OR 1.62, 95% CI 1.02-2.58) with induction. There was no difference in mode of delivery or rates of complications among multiparas.

CONCLUSION

Among women who reach full dilation, labor proceeds similarly regardless of induction status. Induced nulliparas may have an increased risk of hemorrhage and cesarean delivery.

LEVEL OF EVIDENCE

II.