Gestational vitamin D concentration and child cognitive development: a longitudinal cohort study in the Environmental influences on Child Health Outcomes Program.

Background: Low vitamin D concentrations are common-especially among those with darker pigmented skin-and are frequently observed during pregnancy. Given its important role in brain development, inadequate gestational vitamin D may impair child cognitive development.

Objectives: We aimed to evaluate associations of gestational vitamin D concentrations with childhood cognitive scores, explore whether this relationship differs by self-reported race, and examine sensitive exposure windows within pregnancy.

Methods: This prospective cohort study included 912 mother-child dyads (37.3% Black, 52.3% White) from the Environmental influences on Child Health Outcomes program. 25-hydroxyvitamin D [25(OH)D] concentrations were measured in prenatal or cord blood collected between 4 and 42 wk gestation (median: 23 wk). Children's cognition was assessed at ages 7-12 y using the NIH Toolbox Cognition Battery. Relationships of 25(OH)D and cognitive scores were examined using mixed-effects linear models adjusted for confounders. Potential sensitive periods were explored by estimating population 25(OH)D patterns across gestation for varying levels of the cognitive outcomes.

Results: Mean gestational 25(OH)D was 23.8 ng/mL (SD: 10.0 ng/mL). Each 10-ng/mL increase was associated with greater overall (β: 1.11; 95% CI: 0.08, 2.14) and fluid cognition scores (β: 1.21; 95% CI: 0.07, 2.34), but not crystallized cognition. Although these associations were not significantly modified by self-reported race, associations appeared stronger in children of Black mothers (β: 2.99; 95% CI: 0.82, 5.16) than those in non-Black mothers (β: 0.43; 95% CI: -0.93, 1.78) for fluid cognition. Early pregnancy may be a critical exposure period, evidenced by the greatest divergence in the pattern of 25(OH)D during this period between the mothers of children in the 90th and those in the 10th percentiles of cognitive outcomes.

Conclusions: Gestational 25(OH)D concentrations were positively associated with cognitive scores, especially in children of Black mothers. Given higher deficiency risk among Black women, vitamin D repletion before or in early pregnancy may be an important strategy for reducing racial disparities in child neurodevelopment.