CREBRF and type 2 diabetes mellitus: Specifically, the study has four main aims: to determine (1) associations of CREBRF genotype with glucose homeostasis and GDM risk in pregnancy; (2) associations of CREBRF genotype with changes in glucose homeostasis and incident pre-DM/T2DM risk postpartum; (3) the extent to which improvements in insulin secretion mediate the pathway between CREBRF genotype and diabetes risk; and (4) to explore associations between genotype, changes in insulin secretion in pregnancy, and risk of adverse birth outcomes.