Expectant mothers with herpes can feel a little safer taking antiviral medications early in their pregnancies, new research in the Journal of the American Medical Association suggests.
An analysis of data from Denmark finds no increased risk of birth defects for mothers who take the medications during their first trimester -- a critical time in pregnancies when birth defects often form.
Genital herpes is a sexually transmitted disease that is not a health risk to most pregnant women or their babies.
Women generally take antiviral medications during the last weeks of their pregnancies to ensure the infection doesn't transmit to their babies during birth. But when women acquire the infection for the first time during their pregnancy, the infection can put the baby at risk.
Although antivirals are considered safe, data on their use in early pregnancy has been limited.
So doctors at Statens Serum Institut in Copenhagen, Denmark, conducted a study to assess the link between acyclovir, valacyclovir, and famciclovir use in the first trimester of pregnancy and birth defects.
The study included 837,795 infants born in Denmark from January 1996 to September 2008, with a focus on babies whose mothers filled prescriptions for herpes medications.
Among 1,804 pregnancies in which acyclovir, valacyclovir, or famciclovir were used in the first trimester, 40 infants (2.2 per cent) had a diagnosis of a major birth defect. That compared with a 2.4-per cent birth-defect rate among pregnancies without the drugs.
After the researchers adjusted for several variables, they still found the medications were not associated with increased risk of birth defects.
"Our study, to our knowledge the largest of its kind, found no significant association between first-trimester exposure to antiherpetic antiviral drugs and major birth defects," the authors write.
The authors say their study has immediate clinical implications and can help support decisions on safety when prescribing antivirals for herpes in early pregnancy.
They note that acyclovir is the most extensively documented antiviral and should therefore be the drug of choice in early pregnancy, while there is still not enough data on valacyclovir and famciclovir.
The authors also suggest that future studies look at whether herpes antiviral medications are linked to higher rates of spontaneous abortion and preterm birth, as well as the effects of the medications during breastfeeding.
