The purpose of this trial is to determine the effective dose of carbetocin which would prevent the occurrence of postpartum uterine atony in 90% of women undergoing an elective cesarean delivery.

Postpartum hemorrhage is a major cause of maternal morbidity and mortality worldwide. Carbetocin have been shown effective in the prevention of uterine atony, which is the leading cause of postpartum hemorrhage. The Society of Obstetricians and Gynecologists of Canada recommends a single 100 mcg dose of carbetocin after elective cesarean delivery to prevent postpartum hemorrhage. However, there is no clear data in the literature regarding the lowest effective dose of carbetocin that should be administered. The use of the minimum effective dose of carbetocin may reduce its side effects, including hypotension, tachycardia, nausea, vomiting and flushing.

In this trial, healthy term pregnant women undergoing elective cesarean delivery under spinal anesthesia will be recruited. The effective dose of carbetocin that will prevent postpartum uterine atony in 90% of the women (ED90) will be determined using a biased coin design up-down sequential allocation method. The determination of the carbetocin ED90 will help the anesthesiologist regarding the optimal dose of carbetocin to administer after elective cesarean delivery to prevent uterine atony.

Inclusion Criteria:

• Healthy pregnant women (ASA I or II)
• Elective cesarean delivery
• Spinal anesthesia
• Term gestation (37 weeks and above)

Exclusion Criteria:

• Multiple gestation
• Known coagulopathy
• Active labour
• Uterine fibroids
• Body mass index > 45
• Emergency cesarean section
• General anesthesia
• Any contraindication to neuraxial anesthesia
• Cardiopathies
• Known allergies to carbetocin
• Patient refusal
• Placenta previa/Placenta accreta
• Hypertensive disease/Preeclampsia/Eclampsia
• Polyhydramnios
• Previous history of uterine atony or postpartum hemorrhage
• Renal or liver disease