Javaid MK et al. (2006) Maternal vitamin D status during pregnancy and childhood bone mass at age 9 years: a longitudinal study. Lancet 367: 36–43

In this longitudinal study, Javaid et al. tested the hypothesis that vitamin D insufficiency in mothers during pregnancy causes effects on their offspring's bone mass—a relationship that has not previously been directly assessed.

Overall, 198 children born in a Southampton, UK hospital during 1991 and 1992 took part in this study. During late pregnancy, concentrations of the mothers' 25(OH)-vitamin D were measured, and their weight, height and information on dietary supplementation were also recorded. After delivery, the babies were weighed and a sample of the umbilical venous blood was analyzed. The children's bone mass was measured at 9-year follow-up.

Mothers who were deficient in vitamin D during late pregnancy had children with a reduced whole-body bone mineral content, bone area and areal BMD at 9 years of age. Height and weight of children at 9 years was not associated with levels of maternal vitamin D during late pregnancy. Predictors of maternal vitamin D concentrations were estimated exposure to ultraviolet-B light and use of vitamin D supplementation. Umbilical concentrations of calcium correlated positively with whole-body bone mineral content of the child at 9 years.

The mechanisms by which maternal vitamin D insufficiency affects the child's bone mass remain unknown; however, the authors suggest that these might involve an impairment of placental calcium transport. The authors conclude that vitamin D supplementation given to pregnant women (particularly if their last trimester is during the winter months) could enhance fetal bone mineral accrual and reduce osteoporotic fracture in their offspring later in life.