Scientists in the U.K. found that 9-year-old kids had higher bone mineral content, as reflected by bone mineral density (BMD) testing, if their mothers had gotten vitamin D supplements while pregnant.
Cooper is a professor at the MRC Epidemiology Resource Center at England's University of Southampton.
The study appears in The Lancet.
Vitamin D's Role
The researchers note that vitamin D deficiency can be commonly seen in healthy pregnant women and the elderly.
Falling Short on Vitamin D
Many people don't get enough vitamin D. Diet and sun exposure are part of the issue, along with age and skin color.
Making vitamin D is harder for people older than 50 and those without light-colored skin. Melanin in darker skin makes it more difficult to make vitamin D from sunlight.
Seasons and geography also matter. Short winter days mean less opportunity to make vitamin D, especially in northern areas.
Vitamin D Study
Cooper's study included 160 white women who had babies in the early 1990s.
Blood tests showed that nearly half of the women didn't have enough vitamin D, which was measured in late pregnancy. The shortfall was slight for 49 women (31%) and bigger for 28 others (18%), who had vitamin D deficiency.
None of the women was assigned to get more vitamin D from diet, supplements, or sun exposure.
Nine years later, the children the women had been carrying when the study started were evaluated with BMD tests.
The study showed lower bone mineral content for kids whose mothers hadn't gotten vitamin D supplementation during pregnancy.
Supplements for Moms?
The researchers are certain that many pregnant women got too little vitamin D.
If those women had taken vitamin D supplements, their kids might have built stronger bones that would be less likely to fracture later in life, the researchers write.
Of course, getting enough vitamin D wouldn't just help the kids' bones. The moms' bones might also benefit.