Both gestational diabetes mellitus(GDM) and pregnancy induced hypertension (PIH) would influence the gestation significantly. However, the causation between these two symptoms remains speculative. 16,404 pregnant women were identified in Harbin, China in this study. We investigated the evaluate the causal effect of GMD on PIH based on the statistic inference theory. The statistical results indicated that GDM might cause PIH. Also, this case study demonstrated that the decrease temperature might also cause hypertension during pregnancy, and the prevalence rate of GDM increased with age. However, the prevalence of diabetes did not show a remarkable difference in varied areas and ages. This study could provide some essential information that will help to investigate the mechanism for GDM and PIH.