Objective-To evaluate the length of the second stage of labor in relation to increasing maternal prepregnancy BMI among nulliparous parturients, and to determine whether route of delivery differs among obese, overweight, and normal weight women reaching the second stage.Methods-We performed a secondary analysis of a multicenter trial of fetal pulse oximetry, conducted among 5,341 nulliparas who were induced or labored spontaneously at 36 weeks or more of gestation. Normal weight was defined as BMI of 18.5-24.9 kg/m 2 , overweight was a BMI of 25.0-29.9 kg/m 2 , and obese was a BMI of 30 kg/m 2 or higher.Results-Of the 5,341 women, 97% had prepregnancy BMI recorded. Of these, 3,739 had a BMI 18.5 kg/m 2 or higher and reached the second stage of labor. Increasing maternal BMI was not associated with second stage duration: normal weight 1.1 hr, overweight 1.1 hr, and obese 1.0 hr (p=0.13) . Among women who reached the second stage, as BMI increased, so did the likelihood that the woman had undergone induction of labor. Even so, the lack of association between Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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