Does length of labor vary by maternal body mass index?

Abstract

MARA GREENBERG, YVONNE CHENG, NAOMI STOTLAND, AARON CAUGHEY, University of California, San Francisco, Department of Obstetrics, Gynecology and Reproductive Sciences, San Francisco, California OBJECTIVE: To examine the lengths of first and second stages of labor among women of varying body mass indices (BMI), to see if different norms should be established. STUDY DESIGN: This is a retrospective cohort study of all term, singleton, vertex, vaginal deliveries at a single institution. The length of first and second stages of labor were compared between four subgroups stratified by prepregnancy body mass index: low (BMI !19.5 kg/m), normal (19.5-25.9 kg/ m), high (26.0-29.9 kg/m), and obese (O30 kg/m). Length of labor was examined using Kaplan-Meier survival curves for each BMI subgroup and stratified by parity and epidural anesthesia use. RESULTS: Of the 17,218 women examined, there were no differences in length of first or second stages of labor by BMI. For nulliparas, the median lengths of first stage ranged between 8.3 and 9.4 hours (p=0.42) and of second stage ranged between 1.2-2.3 hours among BMI subgroups (p=0.63). When stratified by epidural use, the lengths of labor also did not differ (Figure). Similar results were observed for multiparas, except for those with epidural anesthesia when a small difference in the length of first stage of labor was seen.