RARRES2 and gestational diabetes: As shown in Fig. 4, both the Asian group (SMD: 1.63; 95% CI: 0.42, 2.84) and the European group (SMD: 0.25; 95% CI: 0.03, 0.46) showed higher circulating chemerin levels among women with GDM, especially in the Asia; and although no heterogeneity was observed in the European group (I2 = 0.0%, P = 0.531), considerable heterogeneity were still found in the Asian group (I2 = 98.0%, P < 0.001).