134: Are higher doses of oxytocin needed for obese women to achieve vaginal delivery?

Abstract

Obesity is a risk factor for cesarean delivery, failed induction of labor and labor dystocia, and prolonged labor curves, especially among women with class III obesity. The objective of our study was to compare oxytocin doses among women achieving vaginal delivery based on BMI class. This is a retrospective cohort study of patients delivering at MedStar Washington Hospital Center and MedStar Georgetown University Hospital between August 1, 2010 and July 1, 2016. The cohort was stratified by delivery BMI class with the normal weight group as the reference. The primary outcome was the mean highest oxytocin rate (mU/min). Secondary outcomes included women receiving a maximum oxytocin rate >20 mU/min, highest oxytocin dose (mU), and mean duration of oxytocin exposure. Comparisons were made by route of delivery subgroups. Differences between the groups were compared using ANOVA, Chi-square and Fisher exact test as appropriate. There were a total of 10, 372 births included in the analysis. Our cohort was comprised of 33% of women who were classified as overweight (BMI 25-29.9) and 53% who were classified as obese (BMI >30.0), 12% of whom had a BMI >40. Among women undergoing an induction of labor, the mean duration of oxytocin augmentation to achieve vaginal delivery in the class III obesity group was 12.76 hours with a cumulative oxytocin dose of 12453.8 mU compared to the reference group that had 9.44 hours of oxytocin use and a cumulative oxytocin dose of 7625.9 (p <.0001). Women in the class III obesity group were significantly more likely to require a maximum oxytocin dose >20 mU/min to achieve a vaginal delivery (24.6% vs 10.4%, p<0.001). Obese women require higher doses of oxytocin to achieve a vaginal delivery. We propose that further research is needed to determine whether higher oxytocin protocols should be considered for obese women.View Large Image Figure ViewerDownload Hi-res image Download (PPT)