Non-obstetric surgery during gestation: Risk factors for lower birthweight

Objective: To assess the risk for preterm birth and low birthweight for women undergoing non-obstetric surgery during gestation. Design: Two perinatal tertiary care centres. Population: Women undergoing non-obstetric surgery during gestation between January 1989 and June 1999. Materials and methods: A chart review was carried out. Cervical cerclages, procedures carried out under local anaesthesia or intravenous sedation, or carried out in combination with Caesarean delivery were excluded. Main outcome measures: Preterm birth (<37 weeks), birthweight. Results: A total of 116 of 69 800 women (0.2%) underwent non-obstetric surgery, with 96 women delivering under our care. Procedures were more commonly carried out in the second trimester (53%), versus the first (23%) or third trimester (24%). Surgery in the second trimester resulted in the lowest rate of preterm birth (11%). The overall preterm birth rate was 21% (20/96), with 13 out of 20 (65%) occurring between 35 and 37 weeks. The mean interval from surgery to delivery was 18.7 weeks. Rates of preterm birth were similar for either intra- versus extra-abdominal procedures, or general versus regional anaesthetic. Use of a general anaesthetic was associated with a significant decrease in birthweight (3053 vs 3515 g, P = 0.01) despite similar gestational ages at delivery (37.6 vs 38.6 weeks, P = 0.08). Multiple linear regression controlled for gestational age showed that general anaesthesia, longer surgery duration, and intra-abdominal procedures were all significant independent risk factors for lower birthweight. Conclusion: While non-obstetric surgery appears to be relatively safe during gestation, general anaesthesia, longer surgery time, and intra-abdominal procedures are associated with lower birthweights.