The researchers believe that improving nutrition during tooth formation and in early childhood could reduce the risk of cavities. They wrote, "Prevention efforts should begin during pregnancy by bolstering maternal nutrition, either through improved dietary intake or supplementation with vitamin D."

Whether taking vitamin D supplements is the answer remains controversial, though.

William B. Grant from the Sunlight, Nutrition and Health Research Center in San Francisco, California, is a long-time supporter of vitamin D supplementation.

"All pregnant and nursing women need to take 4,000-5,000 (International Units per day) of vitamin D3. There are many benefits for pregnancy outcomes including reduced risk of gestational diabetes, respiratory and other infections, premature delivery, pre-eclampsia, adverse effects on the fetus such as birth defects including very possibly autism," he says.

A grant has been funded by The Vitamin D Society and the Vitamin D Council to study the benefits of the vitamin, according to his organization's website.

But Philippe P. Hujoel from the University of Washington School of Dentistry in Seattle disagrees that all pregnant women need vitamin D supplements.

"In place of supplementation, I would recommend maintaining proper vitamin D levels during pregnancy the natural way－enjoy the sun and choose foods such as wild salmon, ahi tuna, mushrooms and eggs. Additionally, reducing carbohydrate intake will reduce the body's need for vitamin D," he says.

"Avoid sugar. It is a necessary fuel for dental cavities and it burns up vitamin D," Hujoel adds.