medwireNews: Findings from a large study indicate that 25-hydroxyvitamin D (25[OH]D) levels during foetal life are not linked to childhood bone health independently of childhood vitamin D exposure.
The study is published in The Lancet Diabetes & Endocrinology, in which commentator Christopher Kovacs (Memorial University of Newfoundland, St John’s, Canada) concludes that “the bulk of available data suggest that vitamin D and calcitriol are not needed to regulate calcium homoeostasis or skeletal development before birth.”
The data were drawn from 5294 mother–child pairs from the Generation R Study for whom 25(OH)D concentrations during mid-pregnancy or at birth were known. Deficiency (<50 nmol/L) was common in this cohort, affecting 49.4% of mothers during pregnancy and 79.4% of children at birth.
As mid-pregnancy 25(OH)D concentrations declined, children’s bone mineral density, bone mineral content (BMC) and bone area at age 6 years significantly increased. Although these correlations were independent of multiple confounders, they lost significance after further adjustment for birth weight and length, gestational age at birth, fat and lean mass, and vitamin D supplementation at 1 year of age.
Mid-pregnancy 25(OH)D concentrations below 50 nmol/L remained significantly associated with increased BMC and bone area at age 6 years after accounting even for these factors. But these associations also disappeared after the researchers adjusted for season-adjusted 25(OH)D levels at the time of bone assessment in 3034 children with this information available.
Likewise, there was no association between 25(OH)D concentrations at birth and bone outcomes at age 6 years after accounting for variables including 25(OH)D concentrations at age 6 years, report Audry Garcia (University Medical Center Rotterdam, the Netherlands) and co-researchers.
In his commentary, Kovacs notes that observational studies may not fully account for confounders such as poor nutrition, obesity and socioeconomic status, which can affect childhood 25(OH)D levels as well as bone health before and after birth via other means.
And he says that, despite the study findings, “vitamin D sufficiency should be maintained during pregnancy because calcitriol becomes important soon after birth when the intestines become the dominant route of calcium delivery.”
By Eleanor McDermid
Lancet Diabetes Endocrinol 2017; Advance online publication
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