Maternal hemoglobin and hematocrit levels during pregnancy and childhood lung function and asthma. The Generation R Study.

Objective: To examine the associations of maternal hemoglobin and hematocrit levels during pregnancy with childhood lung function and asthma, and whether adverse pregnancy outcomes and atopic predisposition modify the associations.

Methods: In a population-based prospective cohort study among 3672 subjects, we measured maternal hemoglobin and hematocrit levels in early pregnancy, and lung function by spirometry and current asthma by questionnaire at age 10 years.

Results: Higher maternal hematocrit levels, both continuously and categorized into clinical cut-offs, were associated with lower forced expiratory flow at 75% of forced vital capacity (FEF ) in children (Z-score (95%CI): -0.