This drug was not teratogenic in mouse, rabbit, or rat at exposures greatly more than human exposure. In a review of 229,101 deliveries to Michigan Medicaid patients, 391 first trimester exposures to acyclovir and 1081 exposures any time during pregnancy were recorded. These exposures included systemic and nonsystemic exposures. A total of 18 birth defects were reported with first trimester exposure (17 expected) and included (observed/expected) 5/4 cardiovascular defects, 1 polydactyly, and limb reductions (Written communication, Franz Rosa, MD, Food and Drug Administration, 1994). There are no controlled data in human pregnancy.

AU TGA pregnancy category B3: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans.

US FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.

Benefit should outweigh risk

AU TGA pregnancy category: B3
US FDA pregnancy category: B

See references

Use is generally considered acceptable

Excreted into human milk: Yes

Comments: Women with active herpetic lesions near or on the breast should avoid nursing.

Systemic exposure following oral administration is low suggesting topical use may be insignificant. Women with active herpetic lesions near or on the breast should avoid nursing; topical use to small areas of the mother's body away from the breast should pose no risk to the infant. Water-miscible cream or gel product applied to the breast as ointments may expose infant to high levels of mineral paraffins via licking.

See references