Mediation analyses indicated that 25(OH)D3 explained 24.7% of the protective effect of the VDR rs731236 variant [Indirect effect= -0.06 (-0.12, -0.01)], and 29.6% of the detrimental effect of VDR rs7975232 and GDM risk [indirect effect = 0.07 (0.03, 0.13)]. This evidence concerns the gene VDR and gestational diabetes.