New York: Mothers-to-be please take note! An increased intake of folate and Vitamin B12 supplements during pregnancy is likely to raise the risk of autism spectrum disorder in children, new research led by an Indian-origin scientist suggests. Folate -- a B vitamin found naturally in fruits and vegetables -- is essential in cell growth and promotes neurodevelopmental growth in the foetus. Deficiencies of this nutrient early in pregnancy has been linked to birth defects. "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," said lead author Ramkripa Raghavan from Johns Hopkins University's Bloomberg School Of Public Health in the US. The findings showed that a very high level of folate doubles the risk of a child developing an autism spectrum disorder -- a neurodevelopmental condition characterised by social impairment, abnormal communication and repetitive or unusual behaviour. Also, a high level of vitamin B12 in pregnant women triples the risk of infants developing the disorder. If both levels of vitamin B12 and folate are extremely high, the risk that a child develops the disorder increases 17.6 times. According to the World Health Organisation, between 13.5 and 45.3 nanomoles per liter is an adequate amount of folate for a woman in her first trimester of pregnancy. "We have long known that a folate deficiency in pregnant mothers is detrimental to her child's development. But excessive amounts may also cause harm. Therefore, we must aim for optimal levels of this important nutrient," said one of the authors M Daniele Fallin, doctoral student at Johns Hopkins University in the US. For the study, the team analysed data from 1,391 mother-child pairs recruited at the time of their child's birth between 1998 and 2013 and followed for several years. The mother's blood folate levels was checked once within the first one to three days of delivery. The researchers found that one in 10 of the women had what is considered an excess amount of folate (more than 59 nanomoles per liter) and six percent had an excess amount of vitamin B12 (more than 600 picomoles per liter). The findings will be presented at the 2016 International Meeting for Autism Research in Baltimore, in the US.