This is a prospective observational study among women at high-risk of postpartum hemorrhage, in their third trimester who are admitted to Labor &Delivery in spontaneous labor, for induction of labor, or for scheduled cesarean section.

Inclusion Criteria:

1. Age ≥ 18 years and able to provide consent

2. Gestational age ≥ 34 weeks

3. ≥ 1 High-risk of postpartum hemorrhage criteria defined as either of:

   1. Nulliparous women admitted for induction of labor with unfavorable cervix (Bishop's score <5)
   2. Prior uterine surgery (> 1 prior cesarean or myomectomy)
   3. Patients undergoing trial of labor after cesarean delivery
   4. History of postpartum hemorrhage
   5. ≥4 previous vaginal deliveries
   6. Multiple gestation
   7. The presence of > 2 uterine fibroids or fibroid > 5 cm on any ultrasound during the pregnancy
   8. Planned magnesium sulfate use
   9. Placenta previa/accreta/increta/percreta

Exclusion Criteria:

1. Receipt of anticoagulation (prophylactic anticoagulation stopped 24 hours prior to sample collection is not an exclusion)
2. Antepartum hemorrhage present on admission (>500cc Estimated Blood Loss (EBL))
3. Coagulation defects
4. Thrombocytopenia with platelets count <100,000
5. Enrolled in the "Tranexamic Acid for the Prevention of Obstetrical Hemorrhage After Cesarean (TXA)" (NCT03364491) study or planned receipt of Tranexamic Acid (TXA) prior to enrollment.

Pregnant women with high risk of postpartum hemorrhage