The risk of adverse pregnancy outcome after bariatric surgery: a nationwide register-based matched cohort study.

OBJECTIVE: The aim of this study was to describe the risk of adverse obstetric and neonatal outcome after bariatric surgery. STUDY
DESIGN: Nationwide register-based matched cohort study of singleton deliveries after bariatric surgery during 2004-2010. Data were extracted from The Danish National Patient Registry and The Medical Birth Register. Each woman with bariatric surgery (exposed) was individually matched with 4 women without bariatric surgery (unexposed) on body mass index, age, parity, and date of delivery. Continuous variables were analyzed with the paired t test and binary outcomes were analyzed by logistic regression.
RESULTS: We identified 339 women with a singleton delivery after bariatric surgery (84.4% gastric bypass). They were matched to 1277 unexposed women. Infants in the exposed group had shorter mean gestational age (274 vs 278 days; P < .001), lower mean birthweight (3312 vs 3585 g; P < .001), lower risk of being large for gestational age (adjusted odds ratio, 0.31; 95% confidence interval, 0.15-0.65), and higher risk of being small for gestational age (SGA) (adjusted odds ratio, 2.29; 95% confidence interval, 1.32-3.96) compared with infants in the unexposed group. No statistically significant difference was found between the groups regarding the risk of gestational diabetes mellitus, preeclampsia, labor induction, cesarean section, postpartum hemorrhage, Apgar score less than 7, admission to neonatal intensive care unit or perinatal death.
CONCLUSION: Infants born after maternal bariatric surgery have lower birthweight, lower gestational age, 3.3-times lower risk of large for gestational age, and 2.3-times higher risk of SGA than infants born by a matched group of women without bariatric surgery. The impact on SGA was even higher in the subgroup with gastric bypass.