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Some pregnant women are still prescribed medications with the potential to harm the fetus

About 120,000 U.S. infants are born each year with a birth defect. Teratogens such as isotretinoin (Retin-A) and lithium are drugs that can increase the risk of birth defects. A new study found that 1 percent of women from eight HMOs, who delivered babies from 1996 through 2000, received a teratogenic drug during pregnancy. Nearly 6 percent of this group received U.S. Food and Drug Administration (FDA) category X or category D drugs during pregnancy. Category X drugs are contraindicated in pregnancy because the risk to the fetus clearly outweighs any benefit. Category D drugs, such as certain antiepileptics, are those whose therapeutic benefits may outweigh the risks.

It's not clear whether women refilled medications that had been prescribed before pregnancy without their doctors' knowledge or without recognizing that they were pregnant. On the other hand, some physicians may not have been aware of the potential risks associated with the medications. Nevertheless, the findings underscore the need to educate women about the risks of taking certain medications during pregnancy and of preventing pregnancy when taking medications with potential for fetal harm, note the researchers.

They analyzed the frequency of use of prescription drugs with a potential for fetal harm for 90 days prior to pregnancy and during pregnancy among the 114,165 pregnant women studied. They found that use of these problematic drugs was higher in the first than in later trimesters. Women who were prescribed a teratogen or category D or X drug in the 90 days before pregnancy were 39 and 4 times, respectively, more likely to be prescribed these medications during pregnancy. Fluconazole, carbamazepine, propylthiouracil, and tetracycline were the most commonly dispensed teratogenic drugs. The most frequently dispensed category D and X drugs included female reproductive hormones, doxycyline, atenolol, secobarbital, and benzodiazepines. The study was led by researchers at the HMO Research Network Center for Education and Research on Therapeutics at Harvard Pilgrim Healthcare, which is supported by the Agency for Healthcare Research and Quality (HS10391).

More details are in "Use of prescription medications with a potential for fetal harm among pregnant women," by Susan E. Andrade, Sc.D., Marsha A. Raebel, Pharm.D., Abraham N. Morse, M.D., and others in the August 2006 Pharmacoepidemiology and Drug Safety 15(8), pp. 546-554.

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