OB/GYN Quarterly Update

Antivirals not linked with birth defects

By William T. Elliott, MD, FACP, Chair, Formulary Committee, Kaiser Permanente, California Division, Assistant Clinical Professor of Medicine, University of California-San Francisco

Young women with herpes infections often are treated with the oral antivirals acyclovir, valacyclovir, or famciclovir. A recent study suggests that these drugs are relatively safe when taken in the first trimester of pregnancy (JAMA 2010;304:859-866).

A population-based historical cohort study was performed reviewing the records of more than 800,000 liveborn infants in Denmark who had no diagnosis of chromosomal aberrations, genetic syndromes, birth defects syndromes with known causes, or congenital viral infections. There were 1,804 pregnancies exposed to acyclovir, valacyclovir, or famciclovir in the first trimester. Of those, 40 infants (2.2%) were diagnosed with major birth defects compared with 19,920 (2.4%) among the unexposed infants (adjusted POR, 0.89; 95% CI, 0.65-1.22).

Broken down by drug, major birth defects were seen with 2% of infants exposed to acyclovir and 3.1% exposed to valacyclovir; exposure to famciclovir was uncommon. There was no association between antiviral drugs and specific types of birth defects. The authors conclude that exposure to acyclovir or valacyclovir in the first trimester of pregnancy was not associated with an increased risk of major birth defects.