Based on these numbers, Pasternak and Hviid concluded that the antiviral drugs were not associated with birth defects.
For women taking acyclovir, the most commonly prescribed antiviral, there were 32 cases of birth defects among 1,561 exposed to the drug (2 percent), compared with 2.4 percent of the birth defects among women not exposed acyclovir, they noted.
Among women taking valacyclovir there were seven cases of birth defects among 229 infants (3.1 percent), a rate that was not significantly higher than that of women not exposed to the drug. For famciclovir, there was one case of a major birth defect among the 26 women taking the drug (3.8 percent), but the researchers note that the use of famciclovir was uncommon.
Further analysis did not find any associations between these antiviral drugs and 13 different subgroups of birth defects. However, Pasternak and Hviid stressed that the number of exposed cases in each subgroup was small.
"Genital herpes is a common sexually transmitted disease in women of reproductive age. Its prevalence in women is actually higher than in men," noted Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City. She called the findings "reassuring for patients who may need to use the medications in the first trimester."
Dr. James L. Mills, an investigator in the Epidemiology Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development and coauthor of an accompanying journal editorial comment that, "herpes viruses are an important problem during pregnancy. Many women are treated but there was, until now, only limited information regarding the possible teratogenicity [ability to harm the fetus] of the treatment."
The Danish study answers one key question: are acyclovir and related compounds adding significantly to the number of c
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