GNAS and gestational diabetes: The methylation level of CpG site 4, 5 and 7 of GNAS DMR were significantly correlated with the presence of GDM (P = 0.003; P = 0.002 for site 5 and 7), furthermore, the methylation levels of sites 5 and 7 were significantly correlated with gestational age (P = 0.027 for both).