Maternal vitamin D levels measured during mid-pregnancy and at delivery are not associated with bone outcomes in offspring at age 6 years, nor are vitamin D concentrations in infants at birth, according to findings from a prospective study.
“The findings from our study provide more conclusive evidence that there is no real association between 25-(OH)D concentrations at or before birth and childhood bone mass, and do not support vitamin D supplementation as a routine antenatal care practice in pregnant women to improve offspring bone mass or bone density in childhood or in later life,” Audry H. Garcia, MD, MSc, of the Generation R Study Group at Erasmus MC, University Medical Center in Rotterdam, the Netherlands, told Endocrine Today. “Childhood 25(OH)D concentrations may be more relevant than fetal 25(OH)D concentrations in determining childhood bone mass.”
Audry H. Garcia
Garcia and colleagues analyzed data from 9,901 mother–child pairs with an expected delivery date between April 1, 2002, and Jan. 1, 2006. Researchers measured maternal 25-hydroxyvitamin D concentrations during mid-pregnancy (median, 20.4 weeks) and fetal 25-(OH)D concentrations in cord blood at birth (median gestational age, 40.1 weeks); participants were defined as severely vitamin D deficient (< 25 nmol/L), deficient (25 nmol/L to < 50 nmol/L) and sufficient ( 50 nmol/L). Total-body bone mineral density, bone mineral content, area-adjusted bone mineral content and bone area were measured via DXA scan in children at a median age of 6.1 years (n = 4,815). Researchers used linear regression analysis to determine any associations between fetal vitamin D concentrations and bone health at age 6 years.
Within the cohort, 49.4% of mothers were vitamin D deficient at mid-pregnancy; 79.4% of infants were vitamin D deficient at birth.
Researchers found that severe maternal 25-(OH)D deficiency during mid-pregnancy was associated with higher bone mineral content in offspring at age 6 years (mean, 4.71 g; 95% CI, 1.09-8.33), as well as larger bone area (mean, 7.54 cm²; 95% CI, 2.99-12.11) vs. mothers with sufficient vitamin D status.
However, in a subgroup of children with available data on 25-(OH)D concentrations at 6 years (n = 3,034), the associations no longer persisted after adjustment for season-adjusted 25-(OH)D concentration in children, according to researchers.
When examining 25-(OH)D concentration at birth as a continuous variable, researchers observed inverse associations between vitamin D status at birth and BMD, bone mineral content and bone area at age 6 years; however, results did no persist after adjustment for vitamin D status in children at age 6 years and other variables, including birth weight, birth length, gestational age at birth, fat mass plus lean mass at DXA scan and vitamin D supplementation at age 1 year.
Researchers observed no interaction between maternal calcium intake, child sex, child weight at age 6 years, gestational age or breast-feeding status with vitamin D levels during mid-pregnancy or offspring vitamin D levels at birth, or with any bone parameters in offspring (P > .05 for all).
“At present, no guidelines or clinical cutoffs are available to define vitamin D deficiency during pregnancy, and no studies have addressed if these might differ from non-pregnant individuals,” Garcia said. “Further research is needed to define vitamin D deficiency during pregnancy, and to explore whether vitamin D supplementation during pregnancy may be beneficial for other health outcomes in the mother or their offspring.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.