Roux-en-Y Gastric Bypass Increases Glycemic Excursions during Pregnancy and Postpartum: A Prospective Cohort Study

Objective Roux-en-Y gastric bypass (RYGB) and pregnancy markedly alter glucose metabolism, but evidence on glucose metabolism in pregnancy following RYGB is limited. Thus, the aims of the Bariatric surgery And consequences for Mother and Baby In pregnancy (BAMBI) study were to investigate interstitial glucose (IG) profiles during pregnancy, risk factors associated with hypoglycemia, and the association between fetal growth and hypoglycemia in pregnant women previously treated with RYGB compared to controls.

Research Design and Methods Twenty-three pregnant women with RYGB and 23 BMI- and parity-matched pregnant controls were prospectively studied with continuous glucose monitoring (CGM) in 1st, 2nd and 3rd trimester, and 4 weeks postpartum. Time in range (TIR) was defined as time with IG: 3.5-7.8 mmol/L. 

Results Women with RYGB were 4 years (IQR: 0–7) older than controls. Pregnancies occurred 30 months (IQR: 15-98) following RYGB, which induced a reduction in BMI from 45 kg/m2 (IQR: 42-54) pre-surgery to 32 kg/m2 (IQR: 27-39) pre-pregnancy. Women with RYGB spent decreased TIR (87.3-89.5% vs. 93.3-96.1%, p<0.01) owing to an approximately two-fold increased time above range, and increased time below range (TBR) throughout pregnancy and postpartum compared to controls. Women with increased TBR had longer surgery-to-conception interval, lower nadir weight, and greater weight loss following RYGB. Finally, women giving birth to small-for-gestational age neonates experienced slightly increased TBR.

Conclusions Women with RYGB are more exposed to hypo- and hyperglycemia during pregnancy compared to controls. Further research should investigate whether hypoglycemia during pregnancy in women with RYGB is associated with decreased fetal growth.