The “24–28 weeks” subgroup, “after 28 weeks” subgroup and the rigorous criteria subgroup indicate that higher serum RBP4 level is related to GDM risk (24–28 weeks subgroup: SMD = 0.561, 95 % CI [0.252, 0.870]; after 28 weeks: SMD = 1.830, 95 % CI [0.580–3.080]; the rigorous criteria subgroup: SMD = 1.388, 95 % CI [0.665, 2.110]). The gene discussed is RBP4; the disease is gestational diabetes.