Factors affecting the dose response to oxytocin for labor stimulation.

For nearly 40 years synthetic oxytocin has been used for labor stimulation by titrating dosage rate to uterine contractions. We used a computerized data base to determine variables affecting the dose response to oxytocin in 1773 pregnancies. Statistically important predictors of required oxytocin dosage included cervical dilatation, parity, and gestational age. Maternal body surface area was found to be associated with a higher oxytocin dosage in women undergoing induction of labor. However, the broad range of the statistical confidence intervals precluded prediction of a given pregnancy's oxytocin requirement.