Maternal hemoglobin and iron status in early pregnancy and risk of respiratory tract infections in childhood: A population‐based prospective cohort study.

Background: Maternal hemoglobin and iron status measures during pregnancy might affect the developing fetal respiratory system leading to adverse respiratory conditions. Our aim was to assess the associations of maternal hemoglobin and iron status measures during pregnancy with the risk of respiratory tract infections in children until 10 years of age. Methods: In a population‐based cohort study among 5134 mother–child pairs, maternal hemoglobin and iron status including ferritin, transferrin, and transferrin saturation were measured during early pregnancy. In children, physician‐attended respiratory tract infections from age 6 months until 10 years were assessed by questionnaires. Confounder‐adjusted generalized estimating equation modeling was applied. Results: After taking multiple testing into account, high maternal ferritin concentrations and low maternal transferrin saturation during pregnancy were associated with an overall increased risk of upper, not lower, respiratory tract infections until age 10 years of the child [OR (95% CI: 1.23 (1.10, 1.38) and 1.28 (1.12, 1.47), respectively)]. High maternal transferrin saturation during pregnancy was associated with a decreased and increased risk of upper respiratory tract infections at 1 and 6 years, respectively, [OR (95% CI: 0.60 (0.44, 0.83) and 1.54 (1.17, 2.02))]. Observed associations were suggested to be U‐shaped (p‐values for non‐linearity ≤.001). Maternal hemoglobin and iron status measures during pregnancy were not consistently associated with child's gastroenteritis and urinary tract infections, as proxies for general infection effects. Conclusion: High maternal ferritin and low transferrin saturation concentrations during early pregnancy were most consistently associated with an overall increased risk of child's upper, not lower, respiratory tract infections. [ABSTRACT FROM AUTHOR]