Neonatal Outcomes of Pregnancy Following Roux-en-Y Gastric Bypass: a Matched Case-Control Study

To compare perinatal outcomes and to assess the predictors of birth weight (BW) after Roux-en-Y gastric bypass (RYGB) to those women unexposed to bariatric surgery.

Singleton births from women submitted to RYGB (BSG) were matched to two control births by maternal age, delivery year, and gender. Control group 1 (CG1) and control group 2 (CG2) were selected according to the prepregnancy body mass index (BMI) < 35 kg/m² and ≥ 35 kg/m², respectively, without previous bariatric surgery.

Fifty-eight pregnancies were evaluated in each group (n = 174). Neonates born after RYGB presented lower BW compared to CG1 (mean difference - 182.3 g; 95% CI - 333; - 31, P = 0.018) and CG2 (mean difference - 306.6 g, 95% CI - 502; - 111, P = 0.02). Although gestational age (GA) was similar (P = 0.219), fetal growth rate (in grams) per gestational week was higher in CG2 (β = 196.27, P < 0.001) vs. BSG (β = 127.65, P < 0.001), irrespective of gestational weight gain (GWG). Pregnancies post-RYGB showed lower GWG, lower BW, and higher prevalence of cesarean section than CG1 and were associated with lower BW, smaller cephalic perimeter, lower prevalence of macrosomia, hypertension, and gestational diabetes than CG2.

Birth weight was higher in neonates from women with higher prepregnancy BMI, as compared to births from women submitted to RYGB, irrespective of GWG. Although nearly half of the RYGB mothers were classified with obesity at conception, those pregnancies were associated with better obstetric and neonatal outcomes than among women with prepregnancy BMI ≥ 35 kg/m² who had never undergone RYGB.