Spontaneous cephalic version and risk factors for persistent breech presentation: a longitudinal retrospective cohort study.

Aims: To address the rate of spontaneous version in breech presentation until term and explore the risk factors for persistent breech presentation diagnosed by the second-trimester ultrasound examination.
Methods: This is a retrospective cohort study of pregnant women with a singleton pregnancy who had their ultrasound examination conducted at the time of 22-26 weeks of gestation in the Guangzhou Women and Children's Medical Center. Cox regressions were applied to determine the strength of association between selected risk factors and persistent breech presentation.
Results: Among 25,313 pregnant women eligible for analysis, the prevalence of breech presentation was 36.8% (9,306/25,313) at 22-26 weeks of gestation, 4.2% (376/8,876) of which would remain in the breech presentation at the onset of labor (adjusted odds ratio [aOR], 0.39, 95% confidence interval [CI], 0.17-0.88). Multiparity (aOR, 0.39, 95% CI, 0.30-0.52) and longer gestational weeks at delivery (aOR, 0.50, 95% CI, 0.44-0.56) were associated with a lower risk of persistent breech presentation (PBP). Female fetus, lateral or fundal placenta, and known uterine malformation was each associated with an increased odd of 1.4 (aOR, 95% CI, 1.11-1.70), 2.4 (aOR, 95% CI,1.50-3.73), 3.1 (aOR, 95% CI, 1.71-5.53) and 8.7 (aOR, 95% CI, 3.84-19.84) times in the persistent breech presentation, respectively.
Conclusion: The prevalence of the breech presentation was 36.8% between 22 and 26 weeks of gestation, and approximately 4% would have been in the persistent breech presentation until the onset of labor. Higher educational attainment, multiparity and longer gestational weeks at delivery were significantly decreasing the risk of persistent breech presentation. While the pregnant women with age >40 years, female fetus, lateral or fundal placenta and known uterine malformation were associated increased risk of persistent breech presentation.