In stratified analyses based on mean BMI of GDM patients, the difference of the chemerin levels between the GDM patients and controls was more significant in the group of mean BMI < 28 (SMD: 1.34; 95% CI: 0.02, 2.66) than that of mean BMI ≥28 (SMD: 1.00; 95% CI: − 0.03, 2.03), but dramatic heterogeneity were still observed in both groups (I2 = 98.2 and 96.8% respectively; P < 0.001) (Fig. 7). The gene discussed is RARRES2; the disease is gestational diabetes.