PPARG and type 2 diabetes mellitus: 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.