Pregnant women are often encouraged to supplement their folic acid intake to prevent birth defects, but too much may also carry risks, according to a new study which links excessive folate and vitamin B12 to a greater risk of autism in the child. But the findings come with important caveats.

Why it matters:

Pregnant women need adequate folate, a type of vitamin B, to promote healthy neurodevelopment of their babies. However, the effects of excessive folate haven’t been well-studied.

The nitty gritty:

From 1998 to 2013, researchers gathered data from nearly 1,400 mother-child pairs enrolled in the Boston Birth Cohort. The researchers asked women about their vitamin intake and measured their blood levels of folate and vitamin B12 after giving birth. Researchers at the Johns Hopkins Bloomberg School of Public Health subsequently analyzed that data and noted that mothers with excessive levels of these nutrients in their blood had a higher risk of their child developing autism. Women with more than four times the adequate amount of folate had double the risk, high B12 levels tripled the risk, and high levels of both increased the risk by 17.6 times. The findings were presented on Wednesday at the International Meeting for Autism Research

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But keep in mind:

This research is being presented at a conference, so it hasn’t gone through peer review. That means its findings should be taken with a grain of salt.

Since the women in the study were predominantly from urban minority populations, generalizing the findings to a population level is tricky. Also, since folate levels in blood are not regularly measured in pregnant women, “we don’t at a population level know what the average amount of folic acid in a pregnant woman might be,” explained Dr. Cynthia Gyamfi-Bannerman, associate professor of obstetrics and gynecology at Columbia University Medical Center Maternal-Fetal Medicine.

What they’re saying:  

While this study adds to our understanding, the medical evidence surrounding the relationship between folic acid and autism is still inconclusive, said Gordon Ramsay, assistant professor in the department of pediatrics at the Emory University School of Medicine. Some studies have found a relationship between lower folic acid intake and risk of autism spectrum disorders, other studies found a relationship between higher folic acid intake and risk of the same. “The literature is completely inconsistent. … It means that we don’t know what the real story is,” he explained.

You’ll want to know:

Vitamins are still important during pregnancy. Researchers found that taking multivitamins three to five times a week during pregnancy was associated with a lower risk of autism.

The American Congress of Obstetricians and Gynecologists recommends that pregnant women get at least 600 micrograms of folic acid daily from all sources. “Staying within the current parameters would be both prudent and important until we have more information to confirm these findings,” said Gyamfi-Bannerman.

The bottom line:

Consuming much more folate or vitamin B12 than the guidelines may be harmful to a developing fetus, but more studies will be needed to bear that out.

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  • I was told my doctor to take folic acid three times a day. Each folic acid pill is 800mcg, equaling to a total of 2400mcg per pay. My concern is if this amount can be harmful for my babies (twins). I started taking the folic acid 3 times a day every since I was 4 months pregnant and now I currently 5 going to 6 months. Can taking 2.4mg = 2400mcg be harming my babies?

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