Washington, Mar 2 : Women with low blood levels of vitamin B12 shortly before and after conception may have children with increased risk of a neural tube defect, according to a new study.

Researchers at the National Institutes of Health, Trinity College Dublin, and the Health Research Board of Ireland have found that women with the lowest B12 levels had five times the risk of having a child with a neural tube defect as compared to those with the highest B12 levels.

Also, the study revealed that women who consumed little or no meat or animal-based foods were the most likely group of women to have low B12 levels, along with women who had intestinal disorders that prevent them from absorbing sufficient amounts of B12.

Neural tube defects are a class of birth defects affecting the brain and spinal cord.

It is already known that taking another nutrient, folic acid, during the weeks before and after conception can reduce a woman''s chances of having a child with a neural tube defect. Folic acid is the synthetic form of the vitamin folate.

"Vitamin B12 is essential for the functioning of the nervous system and for the production of red blood cells," said Dr. Duane Alexander, director of the National Institute of Child Health and Human Development.

He added: "The results of this study suggest that women with low levels of B12 not only may risk health problems of their own, but also may increase the chance that their children may be born with a serious birth defect."

For the study, the researchers analysed stored blood samples originally collected during early pregnancy from three groups of Irish women between 1983 and 1990. During that time, pregnant women in Ireland rarely took vitamin supplements.

They explained that the lack of routine vitamin supplementation would enable them to identify a sufficient number of women with low Vitamin B12 to conduct their analysis.

As low folate levels are a known risk factor for neural tube defects, the researchers used statistical techniques to evaluate the role of Vitamin B12 independently of the role of folate.

It was found that women with low B12 concentrations (estimated at less than 250 ng/L, before pregnancy) had 2.5-3 times the risk of having a child with a neural tube defect compared to those with higher levels.

Women with levels in the deficient range (0-149 ng/L ) were at the highest risk: 5 times that of women with higher levels.

Scientists said that it is not known how B12 and folate might interact to influence the formation of the neural tube, the embryonic structure that gives rise to the spine and brain.

They pointed out that the two vitamins are jointly involved with several key biochemical reactions, as well as with the synthesis of DNA.

Lack of either Vitamin B12 or folate in any of these chemical processes theoretically could increase the risk of a neural tube defect.

An NICHD author of the paper said that as Vitamin B12 comes from foods of animal origin, women who adhere to a strict vegan diet may be at risk for a B12 deficiency.

He added it is advisable for women with digestive disorders that interfere with the absorption of foods to consult a physician before getting pregnant, to make sure they are receiving adequate amounts of B12.

"Our results offer evidence that women who have adequate B12 levels before they become pregnant may further reduce the occurrence of this class of birth defects," wrote the authors.

The study appears in the journal Pediatrics. (ANI)