What's the maximum oxytocin dose needed to avoid uterine rupture?

Women having a vaginal birth after a previous cesarean delivery should receive a maximum oxytocin dose of 20 mU/min to avoid uterine rupture, according to a report in the July issue of the American Journal of Obstetrics and Gynecology. A related study in the same issue found that the risk of uterine rupture in these patients cannot be predicted by factors available before admission.

In the first study, Alison G. Cahill, MD, and colleagues from Washington University School of Medicine in St. Louis, analyzed data from 272 women with a previous cesarean delivery and having a vaginal birth and exposed to oxytocin, of whom 62 had a uterine rupture. They found that maximum oxytocin doses above 20 mU/min greatly increased the risk of rupture (hazard ratio 3.92 for 21-30 mU/min; hazard ratio 4.57 for 31-40 mU/min).

In the second study, William A. Grobman, MD, from Northwestern University in Chicago, and colleagues developed a model for uterine rupture using data from 11,855 women with a previous cesarean delivery who underwent labor with a term singleton, of whom 83 (0.7%) had a uterine rupture. They found that any previous vaginal delivery was associated with a lower risk (odds ratio 0.44) and induction of labor was associated with a higher risk (OR, 1.73), but the model was poor (c-statistic of 0.627) and did not provide a useful estimate of the probability of rupture for an individual patient.
“The vaginal birth after Caesarean rate continues to fall in the United States, and many, myself included, believe that this trend is not in the best interest of our patients,” George A. Macones, MD, from Washington University in St. Louis, writes in an accompanying editorial. “Several recent publications…provide us with the ammunition to take an evidenced-based approach to such patients.”

Cahill

AG,

Waterman

BM,

Stamilio

DM, et al. Higher maximum doses of oxytocin are associated with an unacceptably high risk for uterine rupture in patients attempting vaginal birth after cesarean delivery.

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Grobman WA, Lai Y, Landon MB, et al. Prediction of uterine rupture associated with attempted vaginal birth after cesarean delivery.

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