This is a single center, double-blind, randomized trial to compare the effects of intrathecal hydromorphone versus intrathecal morphine to treat post cesarean pain in patients with OUD taking buprenorphine. Inclusion criteria include American Society of Anesthesiologists (ASA) Physical Status II or III presenting for cesarean delivery to be done under spinal anesthesia, who have a diagnosis of OUD and are taking buprenorphine. Exclusion criteria include contraindication to spinal anesthesia, allergy/intolerance to acetaminophen or ibuprofen and laboring patients who have an epidural that will be used for anesthesia for cesarean delivery. Potential subjects will be approached about participating in the study at either their preop anesthesia visit or on the day of surgery after surgical and anesthesia consent has been obtained. Enrolled patients will be randomly allocated to receive either 200 mcg of intrathecal morphine or 100 mcg of intrathecal hydromorphone (study opioid medication). Intraoperatively, with the patient in a sitting position a spinal block will be performed with administration of 0.75% bupivacaine in 8.25% dextrose, 15 mcg fentanyl and the study opioid medication. Supplemental intraoperative analgesia/anxiolysis will be administered at the discretion of the anesthesia care team. Ultrasound-guided transversus abdominis plane blocks will be performed bilaterally at the end of the procedure with 10mL liposomal bupivacaine mixed with 10mL 0.25% bupivacaine injected on each side. Post-cesarean multimodal pain regimen will include scheduled acetaminophen 650mg every 6 hours and scheduled ibuprofen 600mg every 6 hours. Oxycodone will be ordered for breakthrough pain, starting at 5mg every 6 hours as needed. Escalation of as needed pain medication will be at the discretion of the anesthesia team. The patient will be followed for the following 36 hours postoperatively. The primary outcome is the patient's pain score with movement at 12 hours. Secondary outcomes include pain scores at rest and with movement at 6 and 24 hours, satisfaction with anesthesia, time to first opioid use, total opioid consumption in 24 and 36 hours, subjective rating of nausea and pruritis over first 24 hours , treatment for nausea or pruritis in 24 and 36 hours, Obstetric Quality of Recovery 10 (ObsQoR10) score, and Global Health Numeric Rating Scale (NRS) score.