Haemoglobin concentrations in pregnancy and respiratory and allergic outcomes in childhood: Birth cohort study.

BACKGROUND: Limited epidemiological evidence suggests that low maternal iron status and anaemia in pregnancy may increase the risk of childhood respiratory and allergic outcomes. OBJECTIVES: To investigate the relation between maternal haemoglobin concentrations in pregnancy and childhood respiratory and allergic outcomes. METHODS: In the Avon Longitudinal Study of Parents and Children (ALSPAC), we examined associations of maternal haemoglobin concentrations (g/dL) in pregnancy with hayfever, eczema, wheezing, doctor-diagnosed asthma, allergic sensitisation and total IgE at 7 years, and with lung function at 8-9 years in the offspring, after controlling for potential confounders (N = 3234-5335). RESULTS: Maternal haemoglobin was not associated with offspring hayfever, eczema, wheezing or asthma. However, the first haemoglobin measurement in pregnancy (<18 weeks' gestation) and the last measurement (>28 weeks' gestation) were negatively associated with allergic sensitisation (adjusted odds ratio [95% CI] per g/dL 0.91 [0.83 to 0.99] and 0.90 [0.83 to 0.98], respectively). The last haemoglobin measurement was also negatively associated with total IgE (adjusted geometric mean ratio 0.94 [0.88 to 0.99]). Anaemia (haemoglobin <11 g/dL) in late pregnancy was negatively associated with forced vital capacity (difference in standard deviation score -0.07 [-0.13 to -0.01]). CONCLUSIONS AND CLINICAL RELEVANCE: Lower maternal haemoglobin in pregnancy may be a risk factor for allergic sensitisation, elevated IgE and lower FVC in childhood, which may reflect effects of lower prenatal iron status. However, maternal haemoglobin was not associated with risk of childhood asthma or other allergic disorders.