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Maternal and cord blood 25(OH)-vitamin D concentrations in relation to child development and behaviour.

BACKGROUND
Animal studies have linked in utero vitamin D exposure to various aspects of offspring brain development. Limited research has translated these findings to humans, and none have employed cord blood to measure exposure late in gestation.


METHODS
Our objective was to examine the associations between maternal 25(OH)D measured at ≤26 weeks' gestation or cord blood 25(OH)D and offspring global development, IQ, achievement, and behaviour in the US Collaborative Perinatal Project (1959-73). This was a secondary analysis of data from a case-cohort study, with 3896 women and children who participated in at least one outcome assessment. Psychologists assessed global development at 8 months, IQ and behaviour at 4 and 7 years, and achievement at 7 years. Multiple linear and logistic regression was used to examine the associations between 25(OH)D and child outcomes, controlling for maternal education, age, parity, race, maternal body mass index, marital status, smoking, gestational age and month of blood draw, and study site.


RESULTS
Positive associations for many outcomes were greatly attenuated upon adjustment for confounders and were generally null. Only IQ at age 7 was associated with both maternal and cord blood 25(OH)D, but the effect estimates were very small (β for 5 nmol/L increment of maternal 25(OH)D = 0.10; [95% CI 0.00, 0.19]).


CONCLUSION
We observed very little indication that maternal or cord blood 25(OH)D are associated with cognitive development, achievement, and behaviour between 8 months and 7 years of age.