Recent studies are leading pregnant women to question everything they thought they knew about folic acid.

woman taking prenantal vitamin
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We've been told for years that folate is crucial for the development of a healthy baby during pregnancy, especially when it comes to preventing birth defects like spina bifida and anencephaly. But now, there's a growing concern that synthetic folic acid may lead to health risks for both mom and baby, including asthma and breast cancer.

First, a quick tutorial on the difference between folate and folic acid: The former occurs naturally in nature, while the latter is man-made.

Pregnant women and those who are considering becoming pregnant should get between 400 to 800 micrograms of folate each day. Breastfeeding moms should get 500 mcg daily. Most women get adequate amounts of folic acid from their multivitamin, which typically contains at least 400 mcg, or from a prenatal vitamin, which contains at least 600 mcg.

The problem comes in when women get too much of this water-soluble B vitamin. Indeed, a so-called overdose of folic acid supplementation has been linked to an increased risk of cancers. One British study found women who took supplemental folic acid were twice as likely to die of breast cancer. Other studies have linked supplemental folate to heart problems, leukemia, and ectopic pregnancy. An inability to absorb synthetic folate has even been linked to miscarriage.

Some studies have also shown taking supplemental folic acid past early pregnancy offers no benefits, and to the contrary, may even put babies at an increased risk of developing asthma.

The takeaway: Folate is crucial before pregnancy and during the first trimester. After that time, it may be wise to make sure you aren't getting too much of a good thing. The best way to get enough folate is through food sources like lentils, legumes, and dark leafy greens. And it's worth noting fortified foods like breakfast cereals do not carry the same risks as they are metabolized differently in the body.

Melissa Willets is a writer/blogger and a mom. Follow her on Twitter (@Spitupnsuburbs), where she chronicles her love of exercising and drinking coffee, but never simultaneously.