Higher maximum doses of oxytocin are associated with an unacceptably high risk for uterine rupture in patients attempting vaginal birth after cesarean delivery
Presented at the 28th Annual Meeting of the Society for Maternal-Fetal Medicine, Dallas, TX, Jan. 28 to Feb. 2, 2008.
Received 26 September 2007; received in revised form 18 December 2007; accepted 3 March 2008. published online 06 May 2008.
Objective
The objective of the study was to more precisely estimate the effect of maximum oxytocin dose on uterine rupture risk in patients attempting vaginal birth after cesarean (VBAC) by considering timing and duration of therapy.
Study Design
A nested case-control study was conducted within a multicenter, retrospective cohort study of more than 25,000 women with at least 1 prior cesarean delivery, comparing cases of uterine rupture with controls (no rupture) while attempting VBAC. Time-to-event analyses were performed to examine the effect of maximum oxytocin dose on the risk of uterine rupture considering therapy duration, while adjusting for confounders.
Results
Within the nested case-control study of 804 patients, 272 were exposed to oxytocin: 62 cases of uterine rupture and 210 controls. Maximum oxytocin ranges above 20 mU/min increased the risk of uterine rupture 4-fold or greater (21-30 mU/min: hazard ratio [HR] 3.92, 95% confidence interval [CI], 1.06 to 14.52; 31-40 mU/min: HR 4.57, 95% CI, 1.00 to 20.82).
Conclusion
These findings support a maximum oxytocin dose of 20 mU/min in VBAC trials to avoid an unacceptably high risk of uterine rupture.
aDepartment of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO
bDepartment of Medicine, Washington University School of Medicine, St. Louis, MO.
Cite this article as: 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. Am J Obstet Gynecol 2008;199:32.e1-32.e5.
Reprints not available from the authors.
This work was supported by Grants R01 HD 35631 and K24 HD01289, both from the National Institute of Child Health and Human Development (to G.A.M.).
ABSTRACT