The purpose of this study is to compare the ability of a sample of uterine muscle tissue to contract in the presence of various drugs. The drugs studied are typically used to contract the uterus when a pregnant patient continues to bleed after delivery. Amongst the uterotonic drugs (used to contract the uterus), namely oxytocin, ergonovine and carboprost, the most effective one to use is not known.

The investigators will be testing uterine muscle samples in the presence of these drugs at various concentrations, to see what their contractility measures over time, as compared with a control sample, in which no drugs will be applied.

Postpartum hemorrhage (PPH) is a major cause of maternal mortality and morbidity. In 80% cases of PPH, the primary cause is failure of the uterus to contract after delivery of the baby, which then requires further treatment of the mother with uterotonic drugs (drugs used to contract uterus and thus prevent bleeding).

Patients participating in this study will be asked to donate a very small sample of uterine tissue during Cesarean section, which will be tested for the ability to contract after treatment with various uterotonic drugs (oxytocin, ergonovine and carboprost) in the laboratory. This information will help us know the effect of these drugs by comparing the contractile capability of the uterine tissue.

Inclusion Criteria:

• Gestational age 37-41 weeks
• Non-laboring patients, not exposed to exogenous oxytocin
• Patients requiring primary Cesarean section
• Cesarean section under spinal anesthesia

Exclusion Criteria:

• Patients who require general anesthesia
• Patient who had previous uterine surgery or Cesarean section
• Patients with placental anomalies
• Emergency Cesarean section in labor
• Patients with bleeding disorders