Uterotonics in elective caesarean delivery: a randomised non-inferiority study comparing carbetocin 20 µg and 100 µg.

Postpartum haemorrhage is the leading cause of maternal mortality worldwide and prophylactic uterotonic drug administration after the delivery of the infant is advised. Carbetocin is recommended as an uterotonic, but the minimum effective dose has not been verified. We compared the efficacy of two doses of intravenous carbetocin (20 µg and 100 µg) in women undergoing elective caesarean delivery. This was a randomised, double-blind, non-inferiority study in women at low risk of postpartum haemorrhage. Carbetocin was administered on delivery of the anterior shoulder of the neonate. Uterine tone was assessed by the obstetrician 2 min and 5 min after carbetocin administration according to an 11-point numerical rating scale (0 = atonic uterus and 10 = firm uterus). The primary outcome was uterine tone 2 min after carbetocin administration. The pre-specified non-inferiority margin was 1 point on the 11-point scale. Secondary outcomes included: uterine tone at 5 min; use of additional uterotonics within 24 h; blood loss; and adverse effects. Data were available for 53 women in the carbetocin-20 group and for 55 women in the carbetocin-100 group. The mean (SD) uterine tone at 2 min was 7.5 (1.9) in the carbetocin-20 group and 8.0 (1.5) in the carbetocin-100 group. The lower limit of the one-sided 95%CI for the mean difference was outside the non-inferiority margin (at -1.1; p = 0.11) meaning non-inferiority of carbetocin 20 µg compared with carbetocin 100 µg could not be confirmed. However, the secondary outcome measures of uterine tone at 5 min, blood loss and use of additional uterotonics were similar in both groups.