Animal studies have shown this drug readily crosses the placenta. Teratogenicity was not seen when administered to animal models throughout the period of major organogenesis. From 1984 to 1999, a Pregnancy Registry established by the manufacturer and the Centers for Disease Control and Prevention (CDC) collected data for 749 pregnancies (756 outcomes) and found the rate of birth defects for women exposed to systemic drug during the first trimester of pregnancy approximated that of the general population. However, given the small size of the registry, the data is not sufficient to evaluate the risk for less common defects or to permit reliable or definitive conclusions regarding the safety of this drug during pregnancy. 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

Comments:
-This drug has been safely used to treat genital herpes in women in all stages of pregnancy.
-Women who acquire genital herpes simplex virus (HSV) during late pregnancy should be managed in consultation with maternal-fetal medicine and infectious-disease specialists.
-Suppressive therapy late in pregnancy has been shown to reduce the frequency of cesarean delivery among women with recurrent genital herpes by diminishing the frequency of recurrences at term; such treatment may not protect against transmission to neonates in all cases.
-Recommended regimen for HSV suppressive therapy in pregnant women with recurrent genital herpes: 400 mg orally 3 times a day starting at 36 weeks gestation.

See references

Adverse effects in breast-feeding infants associated with exposure to this drug via breast milk have not been reported in the literature. With the highest maternal dosage, the expected infant dose is about 1% of a typical infant dose.

Use caution

Excreted into human milk: Yes

Comments: This drug has been used without apparent harmful effects

See references