(289) Is duration of labor during induction termination associated with adverse maternal outcomes?

Though duration of labor is associated with adverse maternal outcomes in term labor, there are scant data to evaluate this association during induction termination (IT). We evaluated the relationship between duration of labor during IT and adverse maternal outcomes.

Study Design:

We performed a retrospective cohort analysis of all individuals undergoing IT with a singleton gestation with no evidence of rupture of membranes, preterm labor, or cervical insufficiency at 3 tertiary care centers in Chicago, IL from 2009-2019. The primary exposure was the duration of labor for complete fetal expulsion in hours, analyzed categorically (duration of labor < 18 hours v. ≥ 18 hours) and continuously. The primary outcome was composite maternal morbidity (i.e., uterine rupture, need for blood transfusion, suspected intraamniotic infection [IAI], and/or intensive care unit admission). Bivariate and multivariate regression analyses were performed. A priori covariates included gestational age and use of mifepristone. Other covariates were included if p < 0.10 on bivariate analysis. Tests of homogeneity were performed based on prior history of cesarean birth. A Kaplan-Meier curve was generated, censoring at the time the primary outcome was met.

Results:

506 individuals were included (Table). When evaluating duration of labor continuously, longer duration was associated with increased frequency of maternal morbidity on bivariate (β coefficient 0.05, 95% CI 0.02-0.07) and multivariate analyses, after additionally adjusting for nulliparity and maternal age (aβ coefficient 0.04, 95% CI 0.02-0.07, see Figure). When evaluating duration of labor categorically, those with labor ≥ 18 hours had an elevated risk for maternal morbidity on bivariate (RR 2.55, 95% CI 1.61-4.06) and multivariate analyses (aRR 2.70, 95% CI 1.70-4.28). Tests of homogeneity showed no difference in risk based on history of cesarean birth.

Conclusion:

Duration of labor is independently associated with risks for adverse maternal outcomes during IT. Further research should evaluate interventions to reduce the duration of labor in the setting of IT.