Excess folate, vitamin B12 in pregnancy ups kids' autism risk

Mothers-to-be, take note! While folate deficiency is bad for the developing foetus, excessive amounts of the supplement and vitamin B12 may increase the risk of your offspring developing autism spectrum disorder, researchers, including one of Indian-origin, have warned.

Women who plan on becoming pregnant are told they need enough of the nutrient folate to ensure proper neurodevelopment of their babies. Researchers from Johns Hopkins University in the US found that if a new mother has a very high level of folate right after giving birth - more than four times what is considered adequate - the risk that her child will develop an autism spectrum disorder doubles.

Very high vitamin B12 levels in new moms are also potentially harmful, tripling the risk that her offspring will develop an autism spectrum disorder, researchers said. If both levels are extremely high, the risk that a child develops the disorder increases 17.6 times, they said.

Folate, a B vitamin, is found naturally in fruits and vegetables, while the synthetic version, folic acid, is used to fortify cereals and breads in the US and in vitamin supplements.

"We have long known that a folate deficiency in pregnant mothers is detrimental to her child's development," said M Daniele Fallin from Johns Hopkins University. "But what this tells us is that excessive amounts may also cause harm. We must aim for optimal levels of this important nutrient," said Fallin.

Folate 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 autism spectrum disorder, researchers said. Despite this push to ensure women get adequate folate, some women still do not get enough or their bodies are not properly absorbing it, leading to deficiencies, they said.

Autism spectrum disorder is a neurodevelopmental condition characterised by social impairment, abnormal communication and repetitive or unusual behaviour. For the study, researchers analysed data from 1,391 mother-child pairs in the Boston Birth Cohort.

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. Researchers found that one in 10 of the women had what is considered an excess amount of folate (more than 59 nanomoles per litre) and 6%had an excess amount of vitamin B12 (more than 600 picomoles per litre).

"This research suggests that this could be the case of too much of a good thing. We tell women to be sure to get folate early in pregnancy," said Ramkripa Raghavan from Johns Hopkins University. With many types of vitamin supplements, the conventional wisdom has been that too much is not harmful, that the body will flush out the excess. That may not be the case with folic acid and vitamin B12, researchers said.