Oxytocin Augmentation in Spontaneously Laboring, Nulliparous Women: Multilevel Assessment of Maternal BMI and Oxytocin Dose.
BACKGROUND
Synthetic oxytocin, the primary tool for labor augmentation, is less effective among obese women, leading to more unplanned cesarean deliveries for slow labor progress. It is not known if obese women require higher doses of oxytocin due to maternal, fetal, or labor factors related to maternal obesity.


OBJECTIVES
This study had two main objectives: (1) examine the influence of maternal body mass index (BMI) on hourly doses of oxytocin from augmentation initiation until vaginal delivery in obese women; and (2) examine the influence of other maternal, fetal, and labor factors on hourly doses of oxytocin in obese women.


STUDY DESIGN
Longitudinal study of a cohort ( N = 136) of healthy, nulliparous, spontaneously laboring obese women (BMI ≥ 30 kg/m2) who received oxytocin augmentation and achieved vaginal delivery. We performed iterative multilevel analyses to examine the influence of maternal BMI and other factors on hourly oxytocin doses.


RESULTS
Maternal BMI explained 16.56% (95% confidence interval [CI] = [13.7, 20.04], p < .001) of the variance in hourly oxytocin doses received in a multilevel model controlling for influence of maternal, fetal, and labor characteristics. Maternal age, gestational age, status of amniotic membranes at hospital admission, and admission cervical dilation examination were not significant; however, neonatal birthweight and cervical dilation at oxytocin initiation were significant predictors of hourly oxytocin dose in these women ( p < .001).


CONCLUSIONS
Even when parturition preparation has progressed adequately for spontaneous labor initiation, there still may be some obesity-related blunting of myometrial contractility and response to oxytocin used for augmentation.
['Carlson|Nicole S|NS|', 'Corwin|Elizabeth J|EJ|', 'Lowe|Nancy K|NK|']
D000328:Adult D015992:Body Mass Index D015331:Cohort Studies D036861:Delivery, Obstetric D004305:Dose-Response Relationship, Drug D005260:Female D006801:Humans D007751:Labor, Induced D007743:Labor, Obstetric D008137:Longitudinal Studies D009765:Obesity D010121:Oxytocin D011247:Pregnancy
oxytocin augmentation labor dose obesity pregnancy