Therefore, future studies should focus on the VDR gene rs7975232. Second, although the associations of VDR genes rs1544410, rs2228570, and rs731236 with GDM were not significant overall, subgroup analysis indicated that matching and year of publication were the most common sources of heterogeneity, suggesting that the quality of study has been improving in recent years and that future studies should try to control confounding by matching important factors such as BMI, age, and race. Here, VDR is linked to gestational diabetes.