If you’re planning a pregnancy or you’re already pregnant, chances are your doctor told you to take a prenatal vitamin with folic acid to prevent neural tube defects like spina bifida and anencephaly.

Yet new research shows that this recommendation may not be a one-size-fits-all approach and may increase the chances that your baby could be born with birth defects.

Here, find out what experts are saying about folic acid, what they recommend women should take instead and how future guidelines may change.

Faulty genes and folate
Guidelines for folic acid were only put into place 22 years ago when women of childbearing age were recommended to take the synthetic form of folate, or vitamin B9.

Yet in recent years, more research has shown the benefit of taking the bioactive form of folate, known as L-5-methyltetrahydrofolate (MTHF).

Researchers have been focusing on the MTHFR gene,which holds the instructions for making the enzyme that controls many of the chemical reactions—known as methylation— in our bodies, said Dr. Alan Christianson, founder of Integrative Health in Scottsdale, Ariz., and co-author of “The Complete Idiot’s Guide to Thyroid Disease.”

“Those reactions affect how we make our brain chemicals, how we get waste out of our body and how we manage our hormones,” he said. “There are so many methylation reactions in the body and they all need this compound to work right.”

When it comes to folate, you can get it both from foods like leafy greens, nuts, seeds, and legumes and in its synthetic form as folic acid from prenatal vitamins, multivitamins and supplements. Both forms need to be converted into the bioactive MTHF for the body to use, but it’s easier to convert when it comes from food.

Because of one or more defects in their MTHFR gene, about 50 percent of women in the U.S are unable to methylate or utilize folate as well. When women can’t fully convert folic acid into folate, they may not be getting the most benefit from folic acid to prevent neural tube defects. In fact, a study published in the journal PLOS One, shows that a common gene variant that prevents folate conversion is a risk factor for neural tube defects.

“When they take regular folic acid in a prenatal vitamin, it doesn’t become an active form of folic acid,” said Dr. Sara Gottfried, an obstetrician and gynecologist in Berkeley, Calif., and author of the New York Times bestseller “The Hormone Cure.”

Instead, by taking MTHF directly, “You’re bypassing the way the gene will either make you or reduce your ability to methylate the folic acid,” Gottfried said.

In women who are heterozygous—meaning they have one normal gene and one affected gene—their ability to utilize folic acid is 50 to 70 percent less than normal. For women who are homozygous and who have two affected genes, it’s reduced to 70 to 90 percent.

Additionally, the folate-to-MTHF conversion process can leave behind toxic byproducts. Studies show this can increase the risk for colorectal cancer and chronic inflammation which can lead to heart disease, stroke, and obesity, Christianson said.

Is MTHF better than folic acid?
You can find out if you have the MTHFR genetic variants through genetic testing. Many women get tested when they find out they’re pregnant or if they’re struggling with infertility, but it’s better to be proactive and get the testing beforehand if you want to know for sure, Gottfried said.

Yet experts say, even if you don’t get tested, it’s a good idea to take MTHF because not only are the MTHFR gene variants common,  but environmental toxins and lifestyle choices (diet, weight, stress) can affect methylation as well.

“If you’re totally normal, and you take the methylated folate, it doesn’t cause any harm,” Gottfried said.

MTHF can also help with anemia, which is common for many women during pregnancy.

Christianson recommends his patients take a supplement of 1,000 micrograms of MTHF as well as 400 to 800 micrograms of folate. Additionally, if you’ve had several miscarriages or have a family history of neural tube defects, MTHF is likely to be better for you.

Although experts believe this new research will eventually change the guidelines for women, some say there’s not a compelling case to do so. In fact, according to an article in the Natural Medicines Comprehensive Database— a resource for health professionals that provides evidence-based reviews of dietary supplements and alternative therapies— there is no evidence that MTHF is any better than folic acid, even in people who have the MTHFR gene variants .

MTHF is available as a prescription and over-the-counter, but it’s more expensive than folic acid, which could be a drawback for some women.

Dr. Sheryl Ross, an OB/GYN at Providence Saint John’s Health Center in Santa Monica, Calif., says that women with MTHFR gene variants should take MTHF, but for others it’s not necessary and will not increase their risk for having a baby with neural tube defects if they take folic acid.

“For the average person, they should probably be ok with diet and a folic acid supplement,” she said.