OBJECTIVE: To test the hypothesis that myometrial thickness predicts the success of external cephalic version.
METHODS: Abdominal ultrasonographic scans were performed in 114 consecutive pregnant women with breech singletons before an external cephalic version maneuver. Myometrial thickness was measured by a standardized protocol at three sites: the lower segment, midanterior wall, and the fundal uterine wall. Independent variables analyzed in conjunction with myometrial thickness were: maternal age, parity, body mass index, abdominal wall thickness, estimated fetal weight, amniotic fluid index, placental thickness and location, fetal spine position, breech type, and delivery outcomes such as final mode of delivery and birth weight.
RESULTS: Successful version was associated with a thicker ultrasonographic fundal myometrium (unsuccessful: 6.7 [5.5–8.4] compared with successful: 7.4 [6.6–9.7] mm, P=.037). Multivariate regression analysis showed that increased fundal myometrial thickness, high amniotic fluid index, and nonfrank breech presentation were the strongest independent predictors of external cephalic version success (P<.001). A fundal myometrial thickness greater than 6.75 mm and an amniotic fluid index greater than 12 cm were each associated with successful external cephalic versions (fundal myometrial thickness: odds ratio [OR] 2.4, 95% confidence interval [CI] 1.1–5.2, P=.029; amniotic fluid index: OR 2.8, 95% CI 1.3–6.0, P=.008). Combining the two variables resulted in an absolute risk reduction for a failed version of 27.6% (95% CI 7.1–48.1) and a number needed to treat of four (95% CI 2.1–14.2).
CONCLUSION: Fundal myometrial thickness and amniotic fluid index contribute to success of external cephalic version and their evaluation can be easily incorporated in algorithms before the procedure.
LEVEL OF EVIDENCE: III
Fundal uterine wall thickness and amniotic fluid index are important predictors of success when selecting candidates for external cephalic version.
From the Department of Obstetrics, Gynecology & Reproductive Sciences, Yale University, New Haven, Connecticut.
Supported by departmental funds.
The authors thank the nurses, fellows, residents, and faculty at Yale-New Haven Hospital, the Department of Obstetrics and Gynecology and Reproductive Sciences, and all the patients who participated in the study.
Corresponding author: Catalin S. Buhimschi, MD, Yale University, Department of Obstetrics, Gynecology & Reproductive Sciences, 333 Cedar Street, LLCI 804, New Haven, CT 06520; e-mail: email@example.com.
Financial Disclosure The authors did not report any potential conflicts of interest.