The aims of this systematic review were to identify the prevalence of hypoglycemia among pregnant women treated with gastric bypass, and risk factors of hypoglycemic events in pregnancy. We searched MEDLINE, EMBASE, Cochrane, and Scopus databases from inception to April 6, 2021. Six studies investigating glucose metabolism in pregnancy following gastric bypass were included (n=330). As assessed by the oral glucose tolerance test and continuous glucose monitoring, 57.6% (95% CI [40.1, 75.1]) of women with gastric bypass were exposed to hypoglycemia during pregnancy. No studies performed the mixed meal test, and no studies reported on risk factors associated with hypoglycemia. Further studies are required to determine the magnitude of hypoglycemia in these women's everyday-life using continuous glucose monitoring and mixed meal test.