For decades, health experts have been recommending that expecting mothers increase their folic acid intake to promote the healthy neurological development of their babies.

But a recent study out of Johns Hopkins University in Maryland found that excess levels of the vitamin in expecting mothers could have the opposite effect, making children as many as two times more susceptible to developing autism.

Here are the answers to some key questions about folate and its effect on pregnant women and their babies.

What is folic acid?

Folic acid is a B vitamin that for decades has been considered essential to the proper neurological development of fetuses, with many studies linking folic acid deficiencies in early pregnancy to birth defects and a greater risk of autism spectrum disorder.

According to Health Canada, the vitamin plays an important role in cell division in the synthesis of amino acids and nucleic acids that promotes the healthy development of the spine, skull and brain of a fetus, especially during the first four weeks of pregnancy.

What’s the difference between folic acid and folate?

Folate and folic acid are both a B vitamin considered essential to the proper neurological development of fetuses.

Folate is the naturally occurring version of the vitamin found in food such as cereals, orange juice and leafy greens. Folic acid is the synthetic form of the vitamin found in multivitamins and other supplements. (Source: Mayo Clinic)

How much folic acid should women take?

Health Canada recommends that all women who might become pregnant take a daily multivitamin containing 0.4 milligrams of folic acid to prepare for a health pregnancy and protect against neural tube defects.

The agency recommends that all women who are of childbearing age take a daily dose of the vitamin because many pregnancies are unexpected.

Women with diabetes, obesity or epilepsy could be at higher risk of having a child with neural defects and should consult their doctors before taking folic acid.

Women should not take more than one milligram of folic acid per day without first consulting a doctor. (Source: Health Canada)

A recent study by University of Toronto researcher Dr. Young-In Kim found that, on average, folate levels among pregnant Canadian women are 2.5 times higher than what doctors consider “very high.”