Maternal iron status during early pregnancy and school‐age, lung function, asthma, and allergy: The Generation R Study

BACKGROUND: Iron deficiency during early life could affect the developing lung and immune system, and influence child's respiratory or allergy outcomes in later life. OBJECTIVE: To examine the associations of maternal iron status during early pregnancy with child's lung function, asthma, inhalant allergic sensitization, and physician‐diagnosed inhalant allergy at school‐age. METHODS: In a population‐based cohort study, among 3825 mother–child pairs, ferritin, transferrin concentrations, and transferrin saturation were measured from maternal venous blood samples during early pregnancy. In children at the age of 10 years, spirometry was used to determine child's lung function, current asthma and physician‐diagnosed inhalant allergy were assessed by questionnaires, and inhalant allergic sensitization was measured by skin prick tests. We used multivariable regression models to examine the associations. RESULTS: After adjustment for gestational age at maternal iron status measurement and sociodemographic or lifestyle‐related confounders, a higher maternal transferrin concentration was associated with a higher risk of physician‐diagnosed inhalant allergy (odds ratio [95% confidence interval]: 1.13 [1.01 to1.26]), but not with lung function, asthma, or inhalant allergic sensitization. This association did not attenuate after further adjustment for maternal hemoglobin levels or early growth factors. We observed no consistent association of maternal ferritin concentrations or transferrin saturation with child's respiratory or allergy outcomes. CONCLUSION: Higher maternal transferrin concentrations during pregnancy, reflecting lower serum iron levels, were associated with an increased risk of child's physician‐diagnosed inhalant allergy but not lung outcomes. Underlying mechanisms and clinical implications need to be explored.