(719) Optimal Mode of Delivery for Term Breech Presentations: Emulating a Target Trial

Objective: Since the pivotal Term Breech Trial, global studies have demonstrated favorable neonatal outcomes for singleton vaginal breech deliveries. Despite changes in guidance from ACOG, current neonatal and maternal outcomes of those undergoing singleton breech deliveries at term in the US remain unknown. Since a randomized controlled trial (RCT) is ethically infeasible, we emulated a target trial to estimate the causal effect of vaginal versus cesarean delivery of term breech presentations in contemporary deliveries in the US.

Study Design: We utilized the US vital records data of non-anomalous, singleton, term breech live births (2015 to 2020). We emulated a target RCT to contrast neonatal and maternal outcomes in vaginal versus cesarean delivery. To address confounding of the mode of delivery, we performed a propensity score (PS) analysis in a 1:5 match of vaginal to cesarean deliveries, and a doubly-robust estimation to account for confounding of the outcomes. Rates of neonatal and maternal complications were compared between the two groups.

Results: Of 434,952 breech births, 4.4% (n = 19,256) were delivered vaginally. Composite adverse neonatal outcomes occurred in 7.6% of vaginal breech and 5.6% of cesarean breech deliveries (PS-matched, doubly robust odds ratio [OR] 1.14; 95% confidence interval [CI] 1.06, 1.22). Neonatal mortality occurred in 0.5% (n = 90) of vaginal and 0.1% (n = 373) of cesarean breech deliveries (OR 3.25; 95% CI 2.78, 3.79). Composite adverse maternal outcomes occurred in 0.3% of the vaginal breech and 0.5% of the cesarean (OR 0.43; 95% CI 0.31, 0.58) deliveries.

Conclusion: In a contemporary cohort of breech births in the US, vaginal delivery of breech presentations is associated with increased risks of composite neonatal adverse outcomes. This risk is over 3-fold higher for neonatal mortality.  Although the findings are broadly similar to the landmark Term Breech Trial, the risks of both neonatal and maternal adverse outcomes are lower in this contemporary cohort. This present-day data should be considered when counseling patients who desire term vaginal breech births.