The goal of this randomized, double-blind clinical trial is to learn if Oxytocin is most effective at achieving adequate uterine tone (important for preventing postpartum hemorrhage) when administered as a bolus or an infusion in patients at high-risk for postpartum hemorrhage in elective cesarean sections. The main questions that will be answered are:

1. Is Oxytocin bolus more effective than Oxytocin infusion at achieving adequate uterine tone at 2 minutes after the baby is born and every minute thereafter?
2. Does Oxytocin bolus cause less maternal side effects than Oxytocin infusion?
3. Does Oxytocin bolus result in less blood loss than Oxytocin infusion in high risk for postpartum hemorrhage patients undergoing elective cesarean sections?

3. Are patients more satisfied with their cesarean section when they receive Oxytocin bolus or Oxytocin infusion?

Researchers will compare the 2 methods of Oxytocin administration, bolus versus infusion, to see which method is more effective or if they are equally effective.

Participants will:

1. Be randomized to receive either Oxytocin bolus or Oxytocin infusion during their cesarean section but after the baby is born.
2. Be asked a question about their experience 2 hours after the surgery.
3. Allow the research team to collect information about how they are doing from their hospital medical records.

Oxytocin is the most commonly used uterotonic agent worldwide to achieve adequate uterine tone and prevent postpartum hemorrhage. Over the past decade, the trend has been towards lowering the dose to reduce oxytocin-related adverse effects including nausea, hypotension, chest pain, EKG changes, and maternal death. However, the optimal strategy for oxytocin administration remains controversial. A prior study was conducted at Stony Brook University Hospital which investigated the difference between bolus versus infusion administration of oxytocin in elective cesarean section patients with a low risk of postpartum hemorrhage (PPH); the results of this randomized, double blinded clinical trial showed that bolus was not superior for adequate uterine tone at 2 minutes when compared to infusion of oxytocin, but blood loss was modestly lower and total oxytocin exposure was substantially lower in the bolus arm. Which makes the most logical next question: Does bolus oxytocin become more clinically meaningful in patients with higher baseline risk for uterine atony or hemorrhage. The investigators aim to address this question with the INBOX-HR study.

INBOX-HR acts as a continuing investigation on the difference between bolus versus infusion administration of oxytocin, specifically for patients that are at a high risk for postpartum hemorrhage. Thus, the purpose of this research study is to compare bolus and infusion administration of oxytocin on parturients at high risk for postpartum hemorrhage undergoing elective cesarean section. The primary objective of this study is to test the hypothesis that administration by bolus vs. infusion results in more rapid achievement of adequate uterine tone in this patient population. Secondary objectives include determining estimated blood loss, prevalence of hypotension, change in heart rate, nausea, vomiting, and patient satisfaction, and 0 - 10 uterine tone score.

Inclusion Criteria:

• Undergoing elective cesarean section under spinal anesthesia or combined spinal anesthesia (CSE)
• Patients must be able to provide written informed consent in either English or Spanish
• Parturient classified as high risk for postpartum hemorrhage as defined by the adapted California Maternal Quality Care Obstetric Hemorrhage Risk Screen

Exclusion Criteria:

• Parturient in labor or ruptured membranes
• Patient does not possess the physical and mental capacity to provide informed consent
• Urgent or emergent cesarean sections
• Patients with a known major coagulopathy
• Patients with significant thrombocytopenia limiting neuraxial anesthesia (<70k)
• Patients on therapeutic anticoagulation at time of procedure
• Patients on the placenta accreta spectrum
• Patients with severe cardiac disease contraindicating oxytocin
• Patients with an allergy to oxytocin