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conotruncal heart defects
neural tube defect
oral clefts

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vitamin a

High doses of vitamin A induce birth defects in laboratory animals. In humans, a chemically-related substancethe acne medication Accutanecauses serious birth defects in 25% of exposed fetuses. Although its role in embryonic development is not fully understood, vitamin A is active in neural crest cell migrationmovement of cells that originate around the neural tube (spinal cord) and contribute to the developing heart, thymus gland and face.

NO HIGHER RISK IN VITAMIN A USERS

Following a report that moderate doses of vitamin A10,000 IU/day might cause birth defects, we looked to 3 Program studies with extensive information on nutritional factors and vitamin supplements taken during pregnancy. These included over 1500 children with oral clefts, conotruncal heart defects and neural tube defects, conditions potentially influenced by vitamin A.

Mothers whose babies had these birth defects were no more likely to have taken vitamin A supplements. Even when compared to women who didn't take any vitamins at all, those taking vitamin A were not at higher risk.

Women who take multivitamins lower their chance of having babies with many types of birth defects. We hope confusion about vitamin A does not deter women from using multivitamins, which may protect their developing babies from birth defects.

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vitamin a facts

picture of vitamins

There are 2 forms of vitamin A:

bullet Retinol or retinyl ester comes from animal sources, chiefly liver. It is stored in fat and can accumulate in the body.
bullet Beta-carotene is produced by plants, such as carrots, and is converted into active vitamin A once in the body. It dissolves in water; excess beta-carotene is rapidly excreted.

Only the retinol form of vitamin A has been linked to birth defects. Since 1991, multivitamins contain mostly the beta-carotene form.

FEW WOMEN TAKE EXTRA VITAMIN A

Apart from multivitamins, few women in our studies took additional vitamin A. Among interviewed mothers of normal infants:

bullet Only 1.2% had used a vitamin A supplement around the time of conception.
bullet Fewer than 5% had intake levels above 10,000 IU/day from supplements and food sources.

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