Shoulder Dystocia and Labor Induction Stratified by Maternal Weight

Abstract

INTRODUCTION: To determine if the odds of shoulder dystocia increase with maternal body mass index (BMI) in induced or augmented compared with spontaneously laboring women. METHODS: Retrospective study of all shoulder dystocia patients who delivered from 1998 to 2010, women in a control group without shoulder dystocia were matched two to one by maternal BMI, age, parity, and diabetic status. Conditional logistic regression models, with and without fetal-weight adjustments, estimated odds ratios for shoulder dystocia, comparing induced or augmented to spontaneously laboring patients for the entire population, and also by the BMI categories of healthy weight (BMI 18.5–24.9 kg/m2), overweight (BMI 25–29.9 kg/m2), and obese (BMI 30 kg/m2 or greater). The level of significance was set at 5%. RESULTS: Included in the study was 57,259 deliveries; 144 shoulder dystocia cases and 288 women in the control group met study criteria. One hundred seven (74%) shoulder dystocia cases were induced or augmented; 37 (26%) labored spontaneously. One hundred thirty-six (47%) women in the control group were induced or augmented; 152 (53%) labored spontaneously. The normal BMI category included 79 shoulder dystocia cases and 158 women in the control group; the overweight category, 36 shoulder dystocia cases and 72 women in the control group; the obese category, 29 shoulder dystocia cases and 58 women in the control group. Across all BMIs, induced patients were 2.85 times more likely to have shoulder dystocia than noninduced patients (95% confidence interval 1.57–6.14; P<.001). After stratifying by BMI, induced normal-weight patients were 2.11 times more likely to have shoulder dystocia than spontaneously laboring normal-weight patients; induced or augmented overweight patients were 4.74 times more likely to have shoulder dystocia than their spontaneously laboring counterparts; and induced or augmented obese patients were 5.64 times more likely to have shoulder dystocia than their noninduced cohorts (Table 1).CONCLUSION: Induction or augmentation appears to be associated with an increased shoulder dystocia risk with increasing maternal BMI.