If you even hint that you might be thinking of trying to have a baby soon, maybe your doctor will l tell you to start taking a folic acid supplement. A daily prenatal vitamin or folic acid supplement beginning a few months before conception has been shown to significantly reduce the risk of spina bifida and other neural tube defects. But it's important to strike the right balance and not allow levels of the vitamin to creep too high, as that could actually raise a child's risk of developing an autism spectrum disorder, according to new research from Johns Hopkins Bloomberg School of Public Health
Researchers analyzed data from 1,391 pairs of mothers and kids in the Boston Birth Cohort. The moms were recruited at the time of their child's birth—between 1998 and 2013—and followed for several years, with the mother's blood folate levels checked once within the first one to three days of delivery
The study found that if a new mother has a very high level of folate (found naturally in fruits and vegetables while the synthetic version, folic acid, is in vitamin supplements and used to fortify cereals and breads in the U.S.) right after giving birth—more than four times what is considered adequate—the risk that her child will develop an autism spectrum disorder doubles. High B-12 levels in new moms are also considered harmful, tripling the risk, while having extremely high levels of both could cause the risk to increase by 17.6 times
A lot of women in the study reported having taken multivitamins—which would include folic acid and vitamin B12—throughout their pregnancies. But the researchers say they don't know why some of them had such high levels in their blood. They suspect the excess could be a result of women eating too many folic acid-fortified foods, taking too many supplements, or being genetically predisposed to absorbing greater quantities of folate or metabolizing it slower
"Adequate supplementation is protective: That's still the story with folic acid," says one of the study's senior authors M. Daniele Fallin, PhD, director of the Bloomberg School's Wendy Klag Center for Autism and Developmental Disabilities. "We have long known that a folate deficiency in pregnant mothers is detrimental to her child's development. But what this tells us is that excessive amounts may also cause harm. We must aim for optimal levels of this important nutrient
More research is needed to determine any further recommendations on supplementing with folic acid when you're expecting. In the meantime, women who are trying to conceive or pregnant are encouraged to talk about what's best for them to their health care provider