When compared with insulin group, the pooled result showed no significant difference between the metformin and insulin groups in LGA infants rate (Pheterogeneity = 0.15, 4 trials, n = 1206, P = 0.31, OR = 0.78, 95%CI [0.49 to 1.25]); in the SGA infants rate (Pheterogeneity = 0.53, 3 studies, n = 1110, P = 0.34, OR = 0.78, 95%CI [0.48 to 1.29]); in hypoglycemia rate (Pheterogeneity = 0.74, 5 trials, n = 1269, P = 0.19, OR = 0.80, 95%CI [0.58 to 1.11]). The gene discussed is INS; the disease is Hypoglycemia.