To test this hypothesis, we selected 15 single nucleotide polymorphisms (SNPs) within 8 representative genes (CYP27A1, CYP27B1, CYP24A1, VDR, RXRA, RXRB, RXRG and GC) encoding the core proteins involved in VD synthesis and catabolism, and performed a case-control study including 964 GDM cases and 1,021 controls to test the association between these polymorphisms and the risk of GDM. Here, CYP27A1 is linked to gestational diabetes.