- Objective The purpose of this study was to investigate the pregnancy outcome of patients after bariatric surgery. Study design A population-based study was performed that compared all pregnancies of patients with and without previous obesity operations between the years 1988 and 2002. Stratified analyses with the Mantel-Haenszel technique and a multiple logistic regression model were performed to control for confounders. Results Of the 159,210 deliveries that were performed during the study period, 298 deliveries were to patients after bariatric operations. No significant differences regarding obstetric characteristics or pregnancy outcome were noted between the open (n = 159) and laparoscopic procedures (n = 139). With the use of a multivariable analysis, the following conditions were associated significantly with a previous bariatric operation: previous cesarean delivery (odds ratios, 1.4; 95% confidence interval, 1.1-2.0; P = .024), fertility treatments (odds ratios, 2.3; 95% confidence interval, 1.6-3.8; P<.001), premature rupture of membranes (odds ratios, 1.9; 95% confidence interval, 1.3-2.7; P = .001), labor induction (odds ratios, 2.1; 95% confidence interval, 1.6-2.7; P<.001), fetal macrosomia (birth weight,>4 kg; odds ratios, 2.1; 95% confidence interval, 1.4-3.0; P<.001), and obesity (odds ratios, 8.8; 95% confidence interval, 6.1-12.9; P<.001). No significant differences were noted between the groups regarding other pregnancy complications such as placental abruption, placenta previa, labor dystocia, or perinatal complications (such as meconium-stained amniotic fluid, perinatal mortality, congenital malformations and low Apgar scores at 1 and 5 minutes). However, there were higher rates of cesarean delivery among the bariatric operation group (25.2% vs 12.2%; odds ratios, 2.4; 95% confidence interval, 1.9-3.1; P<.001). When controlled for possible confounders (such as previous cesarean delivery, obesity, fertility treatments, premature rupture of membranes, labor induction, diabetes mellitus, hypertensive disorders and fetal macrosomia) by the Mantel-Haenszel technique, the correlation between previous bariatric surgery and cesarean delivery remained significant. Conclusion Previous bariatric surgery, although an independent risk factor for cesarean delivery, is not associated with adverse perinatal outcome.