Success rate of external cephalic version in relation to the woman's body mass index and other factors-a population-based cohort study.

Introduction: The aim of this study was to evaluate the impact of women's body mass index (BMI) on the probability of a successful external cephalic version (ECV).

Material And Methods: A retrospective population-based observational study including all women that underwent an ECV in the southeast region of Sweden from January 2014 to December 2019. Data were collected from electronic medical records, Obstetrix, Cerner. The women were divided into BMI categories according to the World Health Organization classification. Women with a BMI below 25 kg/m formed the reference group. Crude and adjusted odds ratios for unsuccessful ECV in each BMI group were calculated using binary logistic regression. Furthermore, the association between maternal characteristics and clinical and ultrasound variables at the time of the ECV and unsuccessful ECV was evaluated.

Results: A total of 2331 women were included. The overall success rate of ECV was 53.4%. Women with a BMI below 25 kg/m had a success rate of 51.3% whereas obese women had a success rate of 58.6%. The risk of an unsuccessful ECV among obese women (BMI ≥30 kg/m ) had an OR of 0.74 (95% CI 0.59-0.94) compared with women with a BMI below 25 kg/m . After adjusting for suitable confounding factors, the association was no longer significant. Higher maternal age, multiparity, higher gestational age, posterior placenta position, polyhydramnios and higher estimated weight of the fetus at the ECV significantly decreased the risk of an unsuccessful ECV.

Conclusions: Maternal obesity does not seem to negatively influence the success rate of ECV. This is a finding that may encourage both caregivers and obese pregnant women to consider an ECV and so avoid a planned cesarean section for breech presentation in this group.