Excess folate in new mums heightens child’s risk of developing ASD


New mothers who are found to have an excessive level of folate right after giving birth run twice the risk of their child developing an autism spectrum disorder (ASD), according to preliminary findings from a new US study

Researchers at Johns Hopkins Bloomberg School of Public Health analysed data from 1,391 mother-baby pairs in the Boston Birth Cohort, which consists predominantly of low-income, urban-minority families. The mothers 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 researchers found that 10 per cent of the women had an excess amount of folate, that is more than four times the amount considered adequate by the World Health Organisation for women in their first trimester. Six per cent of the women also had an excess amount of vitamin B12. Very high vitamin B12 levels in new mothers are also potentially harmful, tripling the risk that the child will develop an ASD. If both folate and B12 levels are extremely high, the risk increases 17.6 times.

Folate, a B vitamin, is essential in cell growth and promotes neurodevelopmental growth. Deficiencies early in pregnancy have been linked to birth defects and to an increased risk of developing an ASD. Women who plan on becoming pregnant are encouraged to supplement their folate levels to offset this risk. Folate is found naturally in fruits and vegetables, while the synthetic version, folic acid, is used to fortify cereals and breads in the US and is also found in vitamin supplements.

A large majority of the mothers in the study reported having taken multivitamins throughout pregnancy but the researchers say they don’t yet know why some of the women had such high levels of folate in their blood. It could be that they consumed too many foods fortified with folic acid, that they took too many supplements, that they are genetically predisposed to absorbing greater quantities of folate or metabolising it slower, or a mixture of all three.

More research is needed, the researchers say, in order to determine just how much folic acid a woman should consume during pregnancy to have the best chance that she will have optimal blood folate levels at the time of birth. With many types of vitamin supplements, the conventional wisdom has been that too much is not harmful, because the body will flush out the excess. However, that may not be the case with folic acid and vitamin B12.

This research suggests that this could be the case of too much of a good thing.

Says study lead author Ramkripa Raghavan, MPH, MSc, a DrPH candidate in the Department of Population, Family and Reproductive Health at the Bloomberg School.

We tell women to be sure to get folate early in pregnancy. What we need to figure out now is whether there should be additional recommendations about just what an optimal dose is throughout pregnancy.


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