Birth Defects Linked to Low Vitamin B12

Study Shows B12 Deficiency May Raise Risk of Spina Bifida and Other Neural Tube Defects

Reviewed by Louise Chang, MD on March 02, 2009

March 2, 2009 -- Women who don't get enough vitamin B12 may have a higher risk of giving birth to a baby with a potentially disabling or fatal birth defect.

A new study shows that women with vitamin B12 deficiency in early pregnancy were up to five times more likely to have a child with neural tube defects, such as spina bifida, compared to women with high levels of vitamin B12.

"Vitamin B12 is essential for the functioning of the nervous system and for the production of red blood cells," says Duane Alexander, MD, director of the National Institute of Child Health and Human Development, which funded the study. "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."

Researchers say the results suggest that women of childbearing age, women in early pregnancy, and women who hope to become pregnant should take steps to ensure their diet includes foods rich in vitamin B12 or take supplements to reduce their risk of vitamin B12 deficiency and birth defects.

Vitamin B12 is found in meat, poultry, milk, eggs, and other fortified foods. Vegans and vegetarians, and women who have intestinal disorders that prevent them from absorbing vitamin B12, are most susceptible to vitamin B12 deficiency. Vegetarian sources of vitamin B12 include fortified breakfast cereals and some fortified vegetarian "meat" products like veggie burgers.

Vitamin B 12 and Pregnancy

Neural tube defects refer to a group of birth defects that affect the brain and spinal cord. The defects include spina bifida, which can cause partial paralysis, and anencephaly, a fatal condition in which the brain and skull are severely underdeveloped.

The synthetic form of the vitamin folate, folic acid, can significantly reduce the risk of neural tube defects. With food fortification, the incidence of neural tube defects has decreased dramatically. Researchers say these results suggest it may also play a role in birth defect prevention.

In the study, published in Pediatrics, researchers compared vitamin B12 levels in blood samples taken from three groups of Irish women between 1983 and 1990 who were pregnant with or previously had a child with a neural tube defect to those in women with healthy pregnancies. The researchers took into account folate levels in their analysis.

In all three groups, women with low vitamin B12 levels (below 250 ng/L) were up to three times more likely to have a child with a neural tube defect than those with higher levels. Women with vitamin B12 deficiency (levels below 150 ng/L) had the highest risk -- five times higher than that of women with higher levels (greater than 400 ng/L).

Researchers say further studies are needed to confirm these results, but the findings suggest that having vitamin B12 levels above 300 ng/L before becoming pregnant may reduce a child's risk of birth defects.

Show Sources


Molloy, A. Pediatrics, March 2009; vol 123: pp 917-923.

News release, American Academy of Pediatrics.

WebMD medical reference: "Vegetarianism and Vegan Diet."

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