Oxytocin utilization for labor induction in obese and lean women

To determine if oxytocin dosage used for labor induction differed in obese and lean women, we analyzed records of patients who underwent term labor induction and delivered vaginally. Each of a cohort of 27 patients with a body mass index (BMI) >40 kg/m2 was matched with a patient with a BMI <28 kg/m2 for gestational age, for birth weight, and for cervical dilatation and fetal station at admission. The oxytocin dose administered during first stage labor was calculated for each patient. In addition to the matched characteristics, there was no difference between groups in parity, frequency of diabetes, epidural anesthesia use, or pharmacologic cervical ripening. Oxytocin utilization was significantly greater in obese women than in lean women. The maximum administration rate was 17.7±4.7 and 13.1±5.0 mU/min, respectively (P=0.001). Oxytocin administered per minute during the first stage of labor was greater in the obese group (11.6±4.8 vs. 8.6±4.1 mU/min; P=0.020). Neither active phase duration nor the maximum rate of dilatation differed significantly between the groups. That obese parturients required more oxytocin than lean women during the first stage of successful labor induction could not be explained by group differences in parity, birth weight, dysfunctional labor, pre-induction dilatation and station, or epidural use.