Previous caesarean section and major complications during surgical abortion: a national multicentre case–control study

OBJECTIVES: To investigate the association between previous caesarean section (CS) and major complications during first- and second-trimester surgical abortion. STUDY DESIGN: We conducted a national retrospective case-control study using prospectively collected data from all MSI Australia surgical abortion facilities between 2016 and 2024. Individuals undergoing surgical abortion between 5+0 and 23+6 weeks' gestation were eligible. Cases were procedures complicated by haemorrhage ≥500 mL, transfusion, uterine perforation, hospital transfer, laparotomy, laparoscopy, or hysterectomy. Each case was matched to four gestation-matched controls (±3 weeks) through a blinded process. A composite severe outcome included hysterectomy, laparotomy, intensive care admission, disseminated intravascular coagulation, or massive haemorrhage (≥2000 mL). Logistic regression estimated adjusted odds ratios (aORs) with 95% confidence intervals (CIs). RESULTS: Among 159 major-complication cases and 636 gestation-matched controls, a history of previous CS was more common among cases than controls. After adjustment for age, gestational age, parity and body mass index, previous CS remained associated with increased likelihood of being a case (aOR 2.6, 95% CI 1.7-4.0). Odds of being a case increased with increasing numbers of previous CS (aOR 2.0 per caesarean, 95% CI 1.5-2.6). Previous CS was more common among composite severe adverse outcome cases than controls (OR 9.56, 95% CI 4.34-21.04). CONCLUSION: A history of previous CS was more common among cases than controls, with the odds of being a case increasing according to the number of prior CS. These findings may assist counselling, pre-procedure assessment and perioperative planning for patients with a history of caesarean birth. IMPLICATIONS: Previous caesarean section was more common among cases than controls, including cases with severe adverse outcomes. Increasing numbers of prior caesarean sections were associated with higher odds of being a case. These findings may inform counselling and perioperative planning.