Making sure that you get enough folic acid, during pregnancy, is one of the most important things you can do to help prevent birth defects.

Groundbreaking work by a team of UK scientists has identified, for the first time, a link between changes in the DNA of newborn babies, folic acid supplementation during pregnancy, and birth weight.

This state-of-the-art 'epigenetic' study, from scientists funded by the World Cancer Research Fund, showed that the levels of a critical metabolite of folic acid, homocysteine, in the blood of newborn babies is linked to modifications of their DNA in key genes and that such modifications might be used to predict birth weight.

Supplementation with the vitamin, folic acid during pregnancy is known to reduce the risk of neural tube defects (birth defects of the brain and spinal cord) such as spina bifida. It also protects against low birth weight, which has numerous short- and long-term consequences. It has been suggested that folic acid, though its metabolism to chemicals such as homocysteine, might secure these clinical effects via DNA methylation.

The Fetal Epigenomics Group, led by Professor William Farrell, Professor of Human Genomics, Institute for Science and Technology in Medicine at the University of Keele,  examined the relationship between folic acid supplementation and its metabolites on DNA methylation in human blood from the umbilical cord, using a state-of-the-art 'microarray' techniques which simultaneously examines methylation at over 27,000 sites in the DNA.

Professor Farrell said: "It has been known for many years that folic acid supplementation is essential for women during pregnancy to reduce the risk of neural tube defects and low birth weight delivery. However, we had little idea as to how this worked. This study is the first to suggest that methylation of particular genes in the baby's DNA may be the key to unlocking the secret of the action of folic acid. "

"Now we have identified which genes might be the link between folic acid and birth weight, we have opened the door to research that may allow doctors to predict the likelihood of low birth weight with greater certainty. Furthermore, it sheds light on the underlying causes of low birth weight and offers the potential to intervene earlier to prevent poor pregnancy outcomes such as premature delivery and pregnancy loss."

Folic acid, sometimes called folate, is a B vitamin (B9) found mostly in leafy green vegetables like kale and spinach, orange juice, and enriched grains. Repeated studies have shown that women who get 400 micrograms (0.4 milligrams) daily prior to conception and during early pregnancy reduce the risk that their baby will be born with a serious neural tube defect by up to 70%.