Is Valtrex Safe During Pregnancy?
Yes, Valtrex (valacyclovir) is safe to use during pregnancy, with clinical data over several decades showing no increased risk of major birth defects compared to the general population. 1
Safety Evidence
The FDA drug label for valacyclovir confirms that clinical data over several decades in pregnant women have not identified a drug-associated risk of major birth defects. 1
Registry data from 111 pregnancies exposed to valacyclovir showed a major birth defect rate of 3.9% (95% CI: 1.3% to 10.9%) across all trimesters, which is consistent with the general population background risk of 2-4%. 1
First-trimester exposure to valacyclovir resulted in a 4.5% rate of major birth defects (95% CI: 0.24% to 24.9%), again within expected population rates. 1
The larger acyclovir registry (valacyclovir's active metabolite) documented 1,246 pregnancy outcomes with a 3.2% major birth defect rate during first-trimester exposure and 2.6% across all trimesters, providing additional reassurance. 1
Clinical Indications for Use
The American College of Obstetricians and Gynecologists recommends valacyclovir 1 g orally twice daily for 7-10 days to treat first-episode genital herpes during pregnancy. 2, 3
For recurrent genital herpes, suppressive therapy with valacyclovir 1000 mg orally twice daily should begin at 36 weeks gestation and continue until delivery. 4, 3
Life-threatening maternal HSV infections (disseminated infection, encephalitis, pneumonitis, or hepatitis) require intravenous acyclovir 5 mg/kg every 8 hours, as the benefits clearly outweigh any theoretical risks. 2, 3
Why Treatment Matters: Disease-Associated Risks
Untreated herpes during pregnancy poses significant risks to the fetus, particularly when infection occurs near delivery. 1
Primary HSV infection acquired in the third trimester carries a 30-50% risk of neonatal transmission, compared to only 1-3% risk with recurrent HSV at term. 2, 3
Primary herpes in the first trimester has been associated with neonatal chorioretinitis, microcephaly, and skin lesions. 1
In rare cases, transplacental transmission can cause congenital infection with microcephaly, hepatosplenomegaly, intrauterine growth restriction, and stillbirth. 1
Evidence Supporting Suppressive Therapy
Valacyclovir suppression starting at 36 weeks significantly reduces HSV shedding and the need for cesarean delivery due to active lesions. 5
A randomized trial of 350 pregnant women showed that valacyclovir 500 mg twice daily from 36 weeks reduced recurrent genital herpes at delivery from 13% to 4% (P = 0.009). 5
HSV detection by culture at delivery was reduced from 9% to 2% with valacyclovir prophylaxis (P = 0.02). 5
Another randomized trial demonstrated that valacyclovir reduced clinical HSV recurrences between 36 weeks and delivery from 27.3% to 10.5% (P = 0.023). 6
Treatment Algorithm
For pregnant women with HSV, follow this approach:
First episode during pregnancy: Valacyclovir 1 g orally twice daily for 7-10 days (alternative: acyclovir 400 mg three times daily for 7-10 days). 2, 3
History of recurrent genital herpes: Start suppressive therapy at 36 weeks with valacyclovir 1000 mg orally twice daily until delivery. 4, 3
Active lesions or prodromal symptoms at labor onset: Cesarean delivery is mandatory, as it reduces transmission risk by approximately 85%. 4, 3
Life-threatening maternal infection: Intravenous acyclovir 5 mg/kg every 8 hours. 2, 3
Critical Caveats
Do not delay suppressive prophylaxis beyond 36 weeks gestation, as the evidence specifically supports initiation at this timepoint. 4
Viral cultures during pregnancy do not predict shedding at delivery and are not routinely indicated. 2
Cesarean delivery does not completely eliminate neonatal HSV risk but significantly reduces it when lesions are present. 4
All infants exposed to HSV during birth require careful follow-up with viral cultures obtained 24-48 hours after birth, but routine acyclovir treatment is not recommended for asymptomatic infants. 2, 3
Special Populations
HIV-infected pregnant women have the same safety profile for valacyclovir, and some experts recommend prophylaxis for those with frequent, severe recurrences. 2, 3
- Immunocompromised patients may require higher doses of acyclovir (400 mg orally three to five times daily), and acyclovir resistance should be suspected if lesions persist during treatment. 2, 3
Maternal Safety Profile
The occurrence of adverse events in pregnant women taking valacyclovir is low at 3.17% (95% CI, 1.24-5.93%). 7
- Acute renal failure occurred in 1.71% of cases but resolved after discontinuation of the drug. 7