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 matched controls.
Research Design and Methods
In total, 23 pregnant women with RYGB and 23 BMI- and parity-matched pregnant controls were prospectively studied with continuous glucose monitoring (CGM) in the 1st, 2nd and 3rd trimester, as well as 4–6 weeks postpartum. Time in range (TIR) was defined as time with IG of 3.5–7.8 mmol/L.
Results
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. TIR was significantly lower throughout pregnancy and postpartum for the RYGB group compared to controls (87.3–89.5% vs. 93.3–96.1%, p<0.01), due to an increase in both time above range and time below range (TBR)(Figure 1). Accordingly, the coefficient of variation was significantly higher in the RYGB group as a result of an increased diurnal glycemic variability. The women treated with RYGB ran significantly lower nocturnal IG (Figure 2), and the mean nocturnal IG significantly decreased as pregnancy advanced for women treated with RYGB. In the postpartum period, the median of mean nocturnal IG increased to a level higher than that of the 1st trimester. In the course of pregnancy, 48% of the women with RYGB spent increased TBR with highest mean TBR in mid-pregnancy (3.1%, SD 4.5). Women with increased time in hypoglycemia 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 tended to spend more time in TBR.
Conclusions
Women with RYGB are more exposed to hypoglycemia during pregnancy compared to matched controls, especially in mid- and late pregnancy. Longer surgery-to-conception interval, a lower nadir weight, and a greater weight loss may be warning signs of hypoglycemia in pregnancy. Further research should investigate whether hypoglycemia during pregnancy in women with RYGB is associated with fetal growth restriction.