Maternal iron intake and iron status during pregnancy and child blood pressure at age 3 years

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Abstract
Background Animal data suggest that maternal iron deficiency during pregnancy leads to lower birth weight and sustained blood pressure elevation in the offspring. In humans, iron deficiency during pregnancy is common and is associated with adverse birth outcomes such as low birth weight. Data are lacking, however, regarding the effects of maternal iron intake and iron status during pregnancy on offspring blood pressure. Our aim was to examine the extent to which lower maternal iron intake, haemoglobin level and mean cell volume (MCV) during pregnancy are associated with higher child systolic blood pressure (SBP) at age 3 years. Methods We studied 1167 participants in Project Viva, a longitudinal cohort study of pregnant women and their children. We estimated first and second trimester maternal iron intake from food frequency questionnaires. We used an electronic laboratory database to identify haemoglobin and MCV levels in pregnancy. We measured child BP up to five times with a Dinamap and used mixed-effects regression models in our analysis. Results Mean (SD) child SBP at 3 years was 92.0 (9.9) mmHg. Adjusting for confounders, for each 10 mg increase in first trimester iron intake, child SBP was not lower, but was in fact 0.4 mmHg higher (95% CI 0.1, 0.7). For second trimester iron intake, and for first or second trimester haemoglobin and MCV levels, we did not find any appreciable association with 3 year SBP. Conclusions In contrast to animal studies, we did not find that lower maternal iron status during pregnancy was associated with higher offspring BP.