Maternal haemoglobin in pregnancy and offspring childhood weight and height trajectories: analysis of a prospective birth cohort study

Background: Both anaemia and high haemoglobin in pregnancy are associated with adverse pregnancy outcomes including foetal growth restriction. The objective of this study was to investigate the associations between maternal haemoglobin in pregnancy and trajectories of length/height and weight from birth through childhood. Methods: Data from 7,597 singleton pregnancies in the Avon Longitudinal Study of Parents and Children (ALSPAC), an ongoing, prospective, UK population-based pregnancy cohort study were used. We examined associations between maternal haemoglobin (overall pregnancy and trimester specific) and offspring length and weight at birth, as well as trajectories of height and weight gain from birth to age 10 years derived from multilevel models. Results: Mean pregnancy haemoglobin was 11.61 g/dL (SD 1.12). For each 1g/dL higher mean overall pregnancy haemoglobin, offspring were on average -0.30 cm shorter (95%CI: -0.35, -0.24, p <0.001), and -97.7 g lighter (95%CI: -110.42, -84.93, p <0.001) at birth when adjusting for potential confounders. Trimester specific inverse associations with birth length and weight were strongest for third trimester haemoglobin. There was evidence of a positive association between maternal haemoglobin levels and offspring height gain up to the age of one year and no strong evidence of associations between pregnancy haemoglobin and childhood weight gain. Conclusions: In high income countries, higher maternal haemoglobin in pregnancy may be a concern, as well as anaemia. Further studies are needed to define ‘high’ haemoglobin in pregnancy and whether monitoring of women with high pregnancy haemoglobin is warranted.