Acyclovir in First Trimester

http://jama.ama-assn.org/cgi/content/abstract/304/8/859

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

Among 1804 pregnancies exposed to acyclovir, valacyclovir, or famciclovir in the first trimester, 40 infants (2.2%) were diagnosed with a major birth defect compared with 19 920 (2.4%) among the unexposed (adjusted POR, 0.89; 95% confidence interval [CI], 0.65-1.22).
It seems quite safe.