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Herpes Drugs in Early Pregnancy not Linked to Birth Defects

Kathleen Blanchard's picture

Findings from researchers show that acyclovir, valacyclovir, and famciclovir, drugs to treat herpes, pose no risk for birth defects in the first trimester of pregnancy. Herpes affects approximately one percent of women in the first three months of pregnancy. Until now safety of the herpes drugs during early pregnancy had not been established.

Copenhagen scientists included 837,795 infants born between January 1996 and September 2008 in Denmark, checking birth registries for birth defects that might be linked to antiviral medications used by women anytime during the first trimester of pregnancy. After adjusting for other factors, the authors concluded herpes drugs may not raise the risk of birth defects.

All of the infants studied were free of chromosomal abnormalities, genetic and birth defect syndromes with known causes, or congenital viral infections. Among the infants studied, acyclovir, valacyclovir, or famciclovir was prescribed in 1,804 pregnancies during the first trimester of pregnancy.

Antiviral Drugs During Pregnancy need more Study

The study was small, and one of the antiviral drugs, famciclovir, was prescribed infrequently. Acyclovir, the most commonly prescribed herpes treatment was not linked to risk of major birth defects. The authors are recommending acyclovir as the drug of choice in early pregnancy, due to inadequate data for famciclovir and valacyclovir.

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The authors also say, "Future research on antiherpetic antivirals and mother-child health should include safety studies with regard to spontaneous abortion and preterm birth, and during breastfeeding."

Prescribing acyclovir during pregnancy was not found to cause birth defects, but more studies are needed. Two of the drugs, famciclovir and valacyclovir require more study because of small study samples.

The findings have "immediate clinical implications and may support informed decisions on safety when prescribing antivirals for herpes infections in early pregnancy", write the authors. "Acyclovir is the most extensively documented antiviral and should therefore be the drug of choice in early pregnancy, while data on valacyclovir and famciclovir are still insufficient."

In an accompanying editorial James L. Mills, M.D., M.S., and Tonia C. Carter, Ph.D., of the National Institutes of Health, Bethesda, Md., cautioned, though the study is helpful, "additional strategies must be developed to resolve the remaining issues. At a time when the health care system in the United States is facing enormous financial challenges, it is important not to ignore any sources of data that could answer critical medical questions." Herpes drugs may not raise the risk of major birth defects during pregnancy, but more studies are needed.

JAMA. 2010;304(8):859-866. doi:10.1001/jama.2010.1206