NEW YORK (Reuters Health) – Pulsatile rather than continuous infusion of oxytocin in women requiring induction of labor confers little benefit, and when used for labor augmentation it is disadvantageous, according to a UK study reported in the American Journal of Obstetrics and Gynecology online November 9.
“In contrast to our original expectation, pulsatile infusion in the induction group did not reduce the incidence of postpartum hemorrhage at delivery or in the postpartum period,” the authors comment. In the augmentation cohort, fewer women achieved full cervical dilatation.
Dr. Rachel M. Tribe, with King’s College London at the St. Thomas’ Hospital Campus, and colleagues explain that continuous exposure to oxytocin can down-regulate oxytocin receptors in myometrial muscle, which may lead to reduced efficacy and risk of postpartum hemorrhage. In theory, this might be avoided by a pulsatile infusion of oxytocin.
To test this they conducted two randomized trials of continuous oxytocin infusion versus pulsatile infusion with about one-sixth the amount of oxytocin; one trial involved 523 women requiring labor induction, and one looked at labor augmentation in 502 women.
For induction, rates of cesarean delivery were not significantly different with the two strategies: 38.3% in the pulsatile group and 37.7% in the continuous group (p=0.903), the team reports. However infusion-to-delivery times were significantly longer with pulsatile infusion than continuous infusion.
There were no differences in rates of uterine rupture, maternal deep vein thrombosis, pulmonary embolism or, as mentioned, postpartum hemorrhage in the two groups.
When used for labor augmentation, pulsatile oxytocin infusion was associated with higher rates of operative delivery (70.1%) than continuous infusion (62.7%), the investigators found. Also, neonatal morbidity was increased.
Dr. Tribe and colleagues conclude, “In summary, while pulsatile protocol for infusion of oxytocin appeared to be as effective as continuous infusion for induction of labor, it was associated with slightly longer infusion to delivery times and therefore of limited benefit clinically. The pulsatile infusion protocol used in the study would not be recommended for augmentation, as cesarean section rates were not reduced and the protocol was associated with increased rates of maternal and neonatal morbidity.”
Reference:
Am J Obstet Gynecol 2011.
