Studies have shown that more and more women are deficient in vitamin D.  That’s not good for women in general, but for mothers-to-be, a new study suggests that it could put their child at risk for learning difficulties.

Taking vitamin D supplements during pregnancy may relieve the problem. "Adequate vitamin D levels among pregnant women may be important for the optimal development of their baby," said lead researcher Andrew Whitehouse, an associate professor and reader in developmental psychopathology at the Telethon Institute for Child Health Research at the University of Western Australia. "However, it is important for the findings of this study to be replicated before any strong conclusions are made."

Vitamin D levels among pregnant women have decreased steadily over the past 20 years, most likely because of less exposure to sunlight, Whitehouse said.

"The effects of lower maternal vitamin D levels on the developing offspring is not fully understood," he said. "The current study found that women with vitamin D insufficiency during pregnancy have an increased risk of having a child with developmental language difficulties."

Whitehouse's team looked at vitamin D levels in more than 700 pregnant women. They also measured their children's behavior at ages 2, 5, 8, 10, 14 and 17.

In addition, the researchers measured language development when the children were ages 5 and 10.

The researchers found that vitamin D levels during pregnancy had no effect on behavioral or emotional problems of the children.

Researchers did find, however, that that there were noteworthy differences in language skills from children whose mothers were deficient in vitamin D while pregnant.

The Whitehouse group found that these children were twice as likely to have language difficulties as children whose mothers had adequate vitamin D levels.

"The findings suggest that there may be a link between maternal vitamin D levels during pregnancy and offspring neurodevelopment," Whitehouse said.

While the study did uncover a possible association between expectant mother’s vitamin D levels and their children’s language development, it did not prove there was a positive cause and effect link.

"If vitamin D insufficiency during prenatal life is a cause of childhood language difficulties -- and this still needs to be determined conclusively -- then vitamin D supplementation of pregnant women may be an important next step," he said.

Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City, thinks that vitamin D is important for pregnant women.

"Women should get their vitamin D levels checked. We would like to correct these deficiencies before pregnancy," she said.

"Luckily, most [pregnant] women are on a prenatal vitamin and it contains 1,200 international units (IU) of vitamin D, so most women are supplemented throughout pregnancy," Wu added.

Women who are deficient in vitamin D may need as much as 10,000 IU a day, she said.

"If you are starting to try to get pregnant, you should start your prenatal vitamin," Wu said. "It has a lot of good things in it that will be onboard when you get pregnant."

Another expert, Dr. Michael F. Holick, a professor of medicine, physiology and biophysics at Boston University School of Medicine, noted that vitamin D deficiency increases the risk for preeclampsia (a condition marked by increased blood pressure and protein in the urine during pregnancy) and the need for a cesarean delivery.

"So, I am not surprised that developmental issues are also a concern for fetuses that are developing in a vitamin D-deficient state," he said.

"Pregnant women should be increasing their vitamin D intake to levels recommended by the Endocrine Society, which is 1,500 to 2,000 IU a day," Holick said.

Sunlight is a natural source for vitamin D. The skin synthesizes the necessary amount of this vitamin in only half an hour of direct photon exposure. But if you need to increase your intake, there are other resources.

Foods such as cod liver oil, fish and shellfish, vitamin D fortified milk and orange juice, eggs, yogurt, and cheese contain vitamin D.

Vitamin D supplements are also an excellent way to increase your intake.

If you are pregnant, have your vitamin D level checked and discuss your specific needs with your obstetrician.