Objective: The purpose of this study was to examine the lengths of the first and second stages of labor among different racial/ethnic groups to determine whether different norms should be established.
Study design: This was a retrospective cohort study of all laboring, term, singleton, vertex deliveries in a single academic institution. Median lengths of first and second stages of labor were compared among 4 racial/ethnic groups: black, Asian, white, and Latina. Kruskal-Wallis, Wilcoxon rank sum tests, and multivariate linear and logistic regression models were performed.
Results: In 27,521 births, the lengths of first stage of labor did not differ significantly among groups in the multivariate analysis. In the second stage of labor, black women had shorter labors, both overall and stratified by epidural use. In the multivariate analysis, when controlled for demographics, parity, epidural, chorioamnionitis, birthweight, delivery year, and labor management, black women had a shorter second stage than did white women (nulliparous women, 22 minutes; multiparous women, 7.5 minutes; P < .001) and lower rates of prolonged second stage (odds ratio, 0.6; P < .001). Nulliparous Asian women had a significantly longer second stage and higher rates of prolonged second stage, and nulliparous Latina women had a shorter second stage, compared with nulliparous white women.
Conclusion: When data are controlled for confounding factors, black women had a shorter length of second stage of labor than did women in other ethnic groups. These differences appear to be clinically significant. This contributes to the support of a multifactorial redefinition of labor curves, which are used widely in the management of labor.