Considering the lack of sufficient evidence about the effect of candidate genes of T2D on GDM and the conflicting results reported, we therefore performed a meta-analysis to assess the association between the most commonly studied polymorphisms in the PPARG, CDKAL1, KCNQ1, IGF2BP2, TCF7L2, KCNJ11, MTNR1B, GCK genes and GDM risk. This evidence concerns the gene CDKAL1 and type 2 diabetes mellitus.