TFRC and gestational diabetes: Increased transferrin receptor concentrations were associated with GDM with an unadjusted odds ratio of 1.32 (95% CI: 0.73 to 2.37; I2 = 99.8%, p(het) = 3.70 × 10−206) (Figure 5 and Figure S12) and an adjusted odds ratio of 1.18 (95% CI: 0.86 to 1.62; I2 = 77.8%, p(het) = 1.11 × 10−2) (Figure 5, Figures S9 and S10).