Research
Obstetrics
Risk factors for uterine atony/postpartum hemorrhage requiring treatment after vaginal delivery

Presented in part as a poster at the 31st annual meeting of the Society for Maternal-Fetal Medicine, San Francisco, CA, Feb. 7-12, 2011.
https://doi.org/10.1016/j.ajog.2013.03.011Get rights and content

Objective

We sought to identify risk factors for uterine atony or hemorrhage.

Study Design

We conducted a secondary analysis of a 3-arm double-blind randomized trial of different dose regimens of oxytocin to prevent uterine atony after vaginal delivery. The primary outcome was uterine atony or hemorrhage requiring treatment. In all, 21 potential risk factors were evaluated. Logistic regression was used to identify independent risk factors using 2 complementary predefined model selection strategies.

Results

Among 1798 women randomized to 10, 40, or 80 U of prophylactic oxytocin after vaginal delivery, treated uterine atony occurred in 7%. Hispanic (odds ratio [OR], 2.1; 95% confidence interval [CI], 1.3–3.4), non-Hispanic white (OR, 1.6; 95% CI, 1.0–2.5), preeclampsia (OR, 3.2; 95% CI, 2.0–4.9), and chorioamnionitis (OR, 2.8; 95% CI, 1.6–5.0) were consistent independent risk factors. Other risk factors based on the specified selection strategies were obesity, induction/augmentation of labor, twins, hydramnios, anemia, and arrest of descent. Amnioinfusion appeared to be protective against uterine atony (OR, 0.53; 95% CI, 0.29–0.98).

Conclusion

Independent risk factors for uterine atony requiring treatment include Hispanic and non-Hispanic white ethnicity, preeclampsia, and chorioamnionitis.

Section snippets

Materials and Methods

We conducted a secondary analysis of a 3-arm double-blind randomized clinical trial of different doses of oxytocin.20 The primary aim of the trial was to evaluate higher doses of oxytocin compared to a standard low-dose oxytocin regimen used for prophylaxis among women undergoing vaginal delivery. Women were randomized to a 10- (standard), 40-, or 80-U dose regimen of oxytocin at vaginal delivery. Women were excluded if they were <24 weeks' gestation, underwent cesarean delivery, had fetal

Results

Our study sample included all 1798 women randomized and analyzed in the primary trial. In all, 658 women were randomized to 80 U of oxytocin, 481 women to 40 U (this arm was terminated at interim review), and 659 to 10 U of oxytocin. The distribution of the population according to characteristics under study is presented in Table 1. Of note, the dose of prophylactic oxytocin did not influence the outcome in the primary trial. The study population consisted of women who were predominantly obese,

Comment

Of 21 demographic and clinical factors examined, maternal race/ethnicity, preeclampsia, and chorioamnionitis were consistent risk factors for uterine atony or postpartum hemorrhage requiring treatment in our cohort of women who underwent vaginal delivery. When we applied a modified model selection strategy that emphasized strength of association over statistical significance, we identified additional risk factors. Prophylactic oxytocin doses did not influence the results as reported in the

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    The authors report no conflict of interest.

    Cite this article as: Wetta LA, Szychowski JM, Seals S, et al. Risk factors for uterine atony/postpartum hemorrhage requiring treatment after vaginal delivery. Am J Obstet Gynecol 2013;209:51.e1-6.

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