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We appreciate the careful and thoughtful comments from Dr Goetzl on our recent article.¹ We thank Dr Goetzl for her comment regarding our analytic techniques. There were no cases of uterine rupture exposed to oxytocin excluded from this analysis, which was distinct from any done previously in the larger cohort from which this nested case-control study was drawn.

With regard to your broader point, that the article is inflammatory, we would respectfully disagree, although we recognize that new data that can impact a change in clinical practice may often feel uncomfortable to practitioners. In light of the fact that uterine rupture cannot be predicted, we believe there is an important role for better patient selection to vaginal birth after cesarean delivery (VBAC) and intrapartum VBAC management to reduce the risk of uterine rupture and improve patient safety. There are limited data on intrapartum management of VBAC trials and–although we acknowledge, as we did at length in the article, that our study is not without weaknesses–we do think there is information to be gained. Dr Goetzl² published an important study that represents the earliest information on the use of oxytocin in VBAC trials. However, as it was an observational study without any adjusted analyses, we thought that perhaps our study may add to the body of knowledge on the subject. In our study, the risk associations are significantly increased over the reference range in a dose-response manner with respect to the increasing ranges of maximum oxytocin exposure and uterine rupture. The confidence intervals for the hazard ratios reflect precision, but do not replace significance tests,³ and would be incorrectly interpreted as insignificant.

Lastly, the use of attributable risk was not meant to replace our estimate of risk association between maximum oxytocin and uterine rupture as it was not our primary statistical measure of the outcome. It was simply used to frame the discussion of our recommendation for a maximum oxytocin threshold in VBAC trials. As we discussed in the article, our recommendation was exactly that: our recommendation, but framed in the context of other clinically encountered acceptable risks. However, the results of our study may be interpreted and mobilized into clinical practice differently by other practitioners.

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References 

1. 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
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2. Goetzl L, Shipp TD, Cohen A, Zelop CM, Repke JT, Lieberman E. Oxytocin dose and the risk of uterine rupture in trial of labor after cesarean. Obstet Gynecol. 2001;97:381–384
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3. Rothman KJ, Greenland S, Lash TL. Modern epidemiology. 3rd ed.. Philadelphia, PA: Lippincott Williams and Wilkins; 2008;
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