774: Effect of increasing oxytocin dose in the obese, advanced maternal age population

Abstract

To investigate the effect of increasing oxytocin dose on likelihood of vaginal delivery following induction or augmentation of labor among gravida with BMI ≥ 30 and advanced maternal age (AMA). In this sub-analysis of a retrospective cohort study, electronic medical records of 619 obese gravida were reviewed for data on maternal characteristics and labor progression, including methods of induction, dosing of induction agents, duration of labor, mode of delivery, and peripartum complications. Obese gravida aged 14-50 years old with term, vertex, singleton deliveries from 1/2012 to 6/2017 were included. Those with multiple gestations, known aneuploidy or fetal demise, no documented maternal weight or BMI, prior cesarean delivery, and prisoners were excluded. The primary outcome was successful induction and/or augmentation of labor, which was defined as a vaginal delivery. Secondary outcomes included adverse neonatal outcomes (APGAR <7 at 5 minutes) and adverse maternal outcomes (chorioamnionitis, postpartum hemorrhage). Comparisons were made between obese gravida who received > or ≤ 20 milliunits/minute of oxytocin. The interaction between AMA and maximum oxytocin dose > 20 milliunits/minute was analyzed. AMA gravida were more likely to be white, married, and multiparous. No statistical interaction was found between age and dose of oxytocin, including after adjusting for parity, race, marital status, diabetes, smoking status, and gestational age. In an unadjusted analysis, age ≥ 35 and dose of oxytocin ≤ 20 milliunits/minute were both individually associated with increased likelihood of vaginal delivery. In an adjusted analysis, age ≥ 35 was no longer significantly associated with successful induction and maximum oxytocin dose ≤20 milliunits/minute remained associated with increased likelihood of vaginal delivery. There were no differences in chorioamnionitis, postpartum hemorrhage, or APGAR scores with increasing oxytocin dose. Dose of oxytocin >20 milliunits/minute was not associated with increased likelihood of vaginal delivery in an obese, AMA population. Dose of oxytocin ≤20 milliunits/minute was associated with an increased likelihood of vaginal delivery, likely related to the labor progression and patient characteristics that led to the increased oxytocin dose.