A meta-analysis of 16 randomized control trials comparing metformin with insulin in pregnancy in women with GDM or T2DM, concluded that metformin lowered the risk of pregnancy-induced hypertension (RR 0.56; 95% CI 0.37–0.85) and total maternal pregnancy weight gain (mean difference − 2.07; 95% CI − 2.88 to − 1.27), while not increased the risk of cesarean section (RR 0.97 95% CI 0.80–1.19) [66]. The gene discussed is INS; the disease is type 2 diabetes mellitus.