Maternal vitamin D in pregnancy and offspring bone measures in childhood: The Vitamin D in Pregnancy study.

Previously we have demonstrated an association between maternal serum 25-hydroxyvitamin D (25(OH)D) during pregnancy and knee-heel length in offspring at birth. However, it is unknown whether maternal serum 25(OH)D is associated with bone measures in childhood. Thus, we aimed to examine associations between 25(OH)D at two stages of pregnancy and offspring bone measures at 11 years. Women were recruited from a single antenatal clinic in Victoria, Australia before 16 weeks gestation and provided two serum samples to determine 25(OH)D status at recruitment and 28-32 weeks gestation. Children and their mothers were followed up at 11 years of age. Children undertook dual energy X-ray absorptiometry scans at the lumbar spine and total body. Maternal 25(OH)D at recruitment (before 16 weeks gestation) was positively associated with the children's bone mineral content and density in boys, but not girls. In boys, a 10 nmol/L (4 ng/mL) increase in maternal 25(OH)D was associated with a median 0.5 g (95% CI 0.1,0.8) and 0.009 g/cm (95% CI 0.001,0.017) increase in bone mineral content and density at the spine, respectively, and a median 0.006 g/cm (95% CI 0.001,0.011) increase in at the total body. There was no sustained associations with 25(OH)D at the later timepoint (28-32 weeks) with any outcome. At age 11 years, maternal 25(OH)D levels during early pregnancy, but not late were positively associated with bone measures in boys, but not girls.