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Folic acid during pregnancy and the risk of birth sefects

4 December, 2000

Drugs that interfere with the body's use of folic acid can increase the risk of a number of birth defects if taken during pregnancy, according to research published in the latest edition of The New England Journal of Medicine.

Researchers at Boston University's Slone Epidemiology Unit studied 15,000 infants to see if the risk of birth defects increases if mothers took medicines known to disrupt the body's breakdown and absorption of folic acid.

Most drugs that can disrupt folic acid are called dihydrofolate reductase inhibitors, and include the cancer drugs aminopterin and methotrexate, and sulfasalazine, an anti-inflammatory drug. Some common anti-epilepsy drugs such as carbamazepine, phenytoin, phenobarbital and primidone can also affect folic acid.

The occurrence of heart defects and oral clefts were roughly tripled if mothers used dihydrofolate reductase inhibitors within the first three months of pregnancy and doubled if the mothers used the epilepsy medicines.

Women of childbearing age are urged to take multi-vitamins to make sure they get enough folic acid. The research found that the vitamins reduced much of the extra risk of birth defects among women using dihydrofolate reductase inhibitors but not among those taking the epilepsy medicines.