Comparison of Postoperative Pain between Patients who underwent Primary and Repeated Caesarean Section: A Prospective Cohort Study

Abstract Background: The presences of differences in post-operative pain are unclear between the primipara who underwent a primary cesarean section and multipara who underwent first repeat cesarean section. The study aimed to explore the possible difference in postoperative pain between primipara and multipara. Methods: A prospective cohort study was carried out, and only women who underwent cesarean deliveries under spinal anesthesia were included. Postoperative patient-controlled intravenous analgesia was performed for all subjects with 0.2 mg/kg hydromorphone and 4 mg/kg flurbiprofen, and the pump was programmed as 2.0 mL/h background infusion, and loading dose of 1 mL with a lockout period of 15 min. Postoperative incision and visceral pain intensity were evaluated using visual analogue scale, and inadequate analgesia was defined as visual analogue scale ≥40 during the postoperative 48 hours. Additionally, the patients’ pain statuses on postoperative week 1 and week 4 were also assessed during follow-up via telephone. Results: From January to May 2017, a total of 168 patients (67 primipara and 101 multipara) were included. The relative risk for multipara to experience inadequate analgesia on incision pain was 0.42 (95% CI: 0.25 to 0.74) compared to primipara. In patients under 30 years old, inadequate analgesia on visceral pain in the multipara was higher than that on the primipara (RR, 3.56 [1.05 to 12.04], P=0.025). There was no significant difference in the combined incidence of inadequate analgesia in both types of pain between the multipara and primipara (33.7%vs.40.2%, P=0.381). No difference was found in PCIA consumption between two groups. (111.1 ± 36.0mL vs. 110.9 ± 37.3mL, P=0.979) Additionally, a significantly higher incidence of pain at 4 weeks after the surgery was noted in the primipara compared to the multipara (62.2%vs.37.7%, P=0.011). Conclusions: Multipara who underwent first repeat cesarean section have lower risk to experience inadequate analgesia on incision pain during the first 48 hours after surgery compared to primipara. While multipara under 30 years may be more prone to experiencing postoperative inadequate analgesia on visceral pain.