Oxytocin dosage changes delivery options for overweight women

The higher a woman's prepregnancy body mass index (BMI), the more likely she is to deliver surgically, but not if she is given a higher dose of oxytocin, according to data presented at the Society for Maternal-Fetal Medicine Pregnancy Meeting, February 7-12, 2011, in San Francisco, California.

Researchers from Rochester, New York, presented a retrospective cohort study of all women who underwent labor induction at term at their institution from October 2007 to September 2008. Of 498 women in the study, 81% delivered vaginally and 19% required cesarean delivery. An inverse relationship between increasing prepregnancy BMI and the likelihood of vaginal delivery was noted. Women with a prepregnancy BMI less than 25 kg/m² had a hazard ratio (HR) for vaginal delivery of 0.98 (95% CI, 0.97-0.99). Those with BMIs between 25.0 kg/m² and 29.9 kg/m² (ie, overweight) had an HR for vaginal delivery of 0.80 (95% CI, 0.65-0.98); those with BMIs greater than or equal to 30 kg/m² (ie, obese) had an HR of 0.79 (95% CI, 0.63-0.98).

Although the same trend occurred in the group given oxytocin 1 mU/min with increases every 45 minutes (ie, for overweight women, HR, 0.66; 95% CI, 0.47-0.92; for obese women, HR, 0.63; 95% CI, 0.44-0.91), it did not occur in the group given a larger dose (2 mU/min with increases every 30 minutes). Overweight women receiving this dose had an HR for vaginal delivery of 0.86 (95% CI, 0.67-1.12); obese women had an HR of 0.90 (95% CI, 0.69 -1.18).