Other studies have reported that low prenatal vitamin D levels could weaken a baby's immune system and increase the risk of asthma and other respiratory conditions, and heart disease.
Hollis recommends that women who are pregnant or want to become pregnant get 4,000 units a day of vitamin D.
Women must take supplements or spend 10 or 15 minutes in the sun during the summer if they are fair-skinned to get this level of vitamin D, Hollis added. It would be difficult to get this many units even from foods rich in vitamin D, such as fatty fish and fortified milk.
In the current study, Morales and her colleagues measured vitamin D levels in 1,820 pregnant women living in four areas of Spain. Most were in their second trimester.
The researchers found that 20 percent of the women were vitamin D-deficient and another 32 percent had insufficient levels of the vitamin.
Morales and her colleagues found that the babies of mothers whose prenatal vitamin D level was deficient scored on average 2.6 points lower on a mental test and 2.3 points lower on a psychomotor test at about 14 months of age than babies of women whose prenatal vitamin D level was adequate.
Differences of between four and five points in these types of neuropsychological tests could reduce the number of children with above-average intelligence (IQ scores above 110 points) by over 50 percent, Morales noted.
The authors took into consideration other factors that could influence babies' mental and motor development, including birth weight, maternal age, social class and mother's education level, and whether or not the mother drank alcohol or smoked during pregnancy.
The study found a link between vitamin D deficiency during pregnancy and babies' brain development, but it did not prove the existence of a cause-and-effect relationship.
To get a better idea of what these differences in developmental scores mean, t
All rights reserved