The SMD and WMD of transferrin saturation in women who had GDM compared to pregnant women without were 1.05% (95% CI: 0.02 to 2.08; I2 = 93.6%, p(het) = 1.73 × 10−7) and 8.30% (95% CI: 1.38 to 15.22; I2 = 90.4%, p(het) = 3.04 × 10−5), respectively (Figure 2, Figures S7 and S8). The gene discussed is TF; the disease is gestational diabetes.