Fertility and pregnancy

Vitamin B12 deficiency linked to birth defects

zone image Pregnant women with low levels of vitamin B12 more likely to have babies born with neural tube defects

Babies born to mothers who have low blood levels of vitamin B12 just before and after the baby is conceived, may have an increased risk of a neural tube defect, according to latest research published today in the journal Pediatrics.

Neural tube defects affect the brain and spinal cord in the earliest stages of pregnancy and can result in babies being born with spina bifida which causes partial paralysis, as well anencephaly, a fatal condition where the brain and skull are severely under developed.

Women who are trying for a baby and in the early stages of pregnancy are currently advised to take folic acid, another B vitamin, which have been found to lower the risk of neural tube defects.

However, in this latest study, scientists measured vitamin B12 and folate levels in blood samples taken from Irish women between 1983 and 1990 and compared them against the babies health records. During this time, pregnant women in Ireland rarely took vitamin suppements.

After taking into account blood folate levels, the study showed that women with low vitamin B12 levels (less than 250ng/ml) had two to three times the risk of having a baby born with a neural tube defect.

Women who were found to be deficient in vitamin B12 before pregnancy (less than 149ng/ml), ran the greatest risk: five times that of women with higher B12 blood levels.

Duane Alexander, director of the National Institute of Child Health in the USA which carried out the study with scientists from Trinity College, Dublin commented:

"Vitamin B12 is essential for the functioning of the nervous system and for the the production of red blood cells. The results of this study suggest that women with with low levels of vitamin B12 not only may risk health problems of their own but also may increase the chance that their children are born with a serious birth defect."

The authors also pointed out that as vitamin B12 naturally occurs in animal derived food such as fish, meat, poultry, milk and eggs, vegetarians need to be aware of the potential risk when planning a pregnancy.

Lead resarcher Dr. James Mills explained that the key events in the formation of the brain and spinal cord occur very early in pregnancy- in the first 28 days after conception- when women often don't realise they are pregnant. He said:

"If a women wait until they realise that they are pregnant before they start taking folic acid, it is usually too late"

He also added:

"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 defect."

This article was published on Mon 2 March 2009

Image © Anatoly Tiplyashin - Fotolia.com

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