Oxytocin infusion rate 16 IU/h for Postpartum Hemorrhage

This study is designed to determine the minimal effective oxytocin maintenance dose required during cesarean delivery to achieve the best effect. Oxytocin is a drug which is routinely used to help contract the uterus and keep it contracted after the delivery of the baby and placenta. The aim of oxytocin is to reduce the amount of blood that might be lost. In order to determine the minimal effective dose, the investigators will conduct a dose-finding study. The first patient will receive a set oxytocin infusion. If the uterus contracts well, this is considered satisfactory and the next patient will receive the same dose. If the uterus does not contract well, this is considered unsatisfactory and the next patient will receive a higher dose. The dose for the next patient will be determined based on the results of the uterine contraction of the previous patient. The investigators hypothesize that the ED90 of an oxytocin infusion rate to maintain a satisfactory uterine tone during a cesarean delivery in non-laboring women, would be lower than that found in previous studies without an initial bolus (less than 16 IU/h).