Similar to the birth weight in the metformin-exposed group, metformin also lowered the risk of macrosomia by 30% compared with the insulin-exposed group based on 20 studies (RR 0.75; 95% CI 0.54, 0.86; I2 = 17%; p = 0.001) (Fig. 2B) [15, 17, 18, 20, 22, 24–38]. Here, INS is linked to Large for gestational age.