Examined metabolic effects of a vegan diet (VD) on pregnant mice.Female-wild-type mice were fed a control diet (CD) or a VD (reduced-B12-content) for 18 weeks and bred twice. Body weights, glucose tolerance, and a marker of B12-insufficiency were measured.VD-mothers only displayed B12 insufficiency, while their female offspring sustained B12-insufficiency, glucose intolerance, and higher body weights. Greater impacts were observed in the second breeding attempt.B12-deficiency induced significant metabolic disturbances in the first generation.