Impact of fetal gender on the labor curve.

Abstract

We sought to estimate the association between fetal gender and first-stage labor curve at term. Within a large, retrospective cohort study of consecutive, singleton term labor patients who delivered in the second stage, we compared the active phase of first-stage labor by fetal gender. The primary outcome was length of active stage 1. Interval-censored regression was used to estimate the effect of fetal gender on the duration of active first stage (4-10 cm) and was adjusted for relevant covariates. Of 2400 women, 2373 women had complete labor information and were available for this analysis. Male gender was associated with both a statistically significantly longer active first stage of labor (4.6 vs 4.0 hours; P = .002) and stratified analyses by parity and labor type. Male fetuses are associated with longer active phase of the first stage of labor and, specifically, may need to be considered in the setting of arrest diagnoses.