Prevention of Postpartum Hemorrhage With Tranexamic Acid

In part 1 of the study, the investigators conducted a prospective, open-label, dose finding pharmacokinetic (PK) study in 43 pregnant 3rd trimester women scheduled for non-emergent cesarean section. The investigators administered three doses of the drug (5 mg/kg, 10 mg/kg and 15 mg/kg) in an escalating fashion by cohort with the lowest dose first. The drug was administered intravenously at the time of umbilical cord clamping for a non-emergent cesarean section. A maximum of 1 g was administered. TXA serum levels at several time points after delivery were assayed to see if they reach the target plasma concentration of 10 ug/mL. A PK model was constructed for determining the optimal TXA dose administered at parturition. In part 2 of the study, the investigators aim to compare PKPD endpoints using prophylactic TXA via IV and IM routes administered pre-cord clamp. The investigators will administer 1 g TXA within 10 minutes of skin incision via intravenous infusion (up to n=15), intravenous bolus \< 2 minutes (up to n=15) and intramuscular injection (up to n=15). The investigators will target women undergoing scheduled cesarean delivery \> 34 weeks gestation, women undergoing vaginal delivery \> 34 weeks of gestation and morbidly obese women (BMI\>=40) undergoing either a vaginal or cesarean delivery. The investigators will use advanced modeling techniques to determine time to achieve PKPD targets and duration remaining at those targets. The goal will be to determine how the optimal dose may vary if route of administration is modified. The investigators plan to enroll 45 patients in addition to the 43 that were enrolled during part 1. Our goal is to 30 participants, but the investigators will enroll 45 to account for lost to follow-up. The investigators also aim to enroll 30 patients undergoing vaginal delivery and 30 morbidly obese women (BMI \>= 40) undergoing either a vaginal or cesarean delivery but the investigators will enroll 45 patients for each of these groups to account for loss to follow up. In addition, the investigators will enroll 30 pregnant patients receiving no medication acting as the control group, but the investigators will enroll 45 to account for loss to follow up.