TFRC and nutritional disorder: There was no impact of iron supplementation on maternal transferrin receptor concentration (average MD ‐0.16; 95% CI ‐0.96 to 0.65; studies = 3; participants = 2,431; random‐effects; Tau2 = 0.46; I2 = 99%; Analysis 6.8); however, iron supplementation improved iron deficiency when compared to placebo (average RR 0.54; 95% CI 0.40 to 0.74; studies = 4; participants = 2,522; random‐effects; Tau2 = 0.06; I2 = 82%; Analysis 6.9).