External cephalic version (ECV) is a procedure used to turn a baby in the womb before delivery. Uterine relaxants are drugs used to facilitate fetal manipulation. Oxytocin receptor antagonist atosiban and beta mimetic fenoterol are the two routinely used uterine relaxants. This study aims to compare the efficacy of atosiban and fenoterol as uterine relaxants for ECV.

This randomized, open-label, multicenter controlled trial included a total of 830 women with a singleton fetus in breech presentation and gestational age of more than 34 weeks. The participants were randomly assigned in a 1:1 ratio to receive either 6.75 mg atosiban (n=416) or 40 μg fenoterol (n=414) intravenously for uterine relaxation before ECV. The primary outcome of the study was a fetus in cephalic procedure 30 minutes after the procedure. Adverse events, like maternal complications and drug-related severe outcomes, were also evaluated.

In the atosiban group, the cephalic position 30 minutes after ECV occurred in 34% of women, as compared with 40% in the fenoterol group. Presentation at birth was cephalic in 35% in the atosiban group and 40% in the fenoterol group.

The research concluded that fenoterol produced better outcomes as a uterine relaxant for ECV, as compared with atosiban. 

Ref: https://www.bmj.com/content/356/bmj.i6773