In the MIG trial, the total B12 vitamin stores (indicated by total circulating levels of B12 vitamin) were depleted during pregnancy (from randomization at 20–34 weeks of gestation to 36 weeks) to a greater extent in metformin-treated than in insulin-treated women with GDM, and the decline in B12 vitamin concentrations was more pronounced in those experiencing a longer treatment duration [126]. Here, INS is linked to gestational diabetes.