Is Valtrex (valacyclovir) safe to use at 30 weeks of pregnancy?

Valacyclovir Safety at 30 Weeks of Pregnancy

Valacyclovir (Valtrex) can be used at 30 weeks of pregnancy if the potential benefit justifies the potential risk to the fetus, as current evidence does not indicate an increased risk of major birth defects. 1

Safety Profile in Pregnancy

The FDA drug label for valacyclovir provides the most authoritative guidance on its use during pregnancy:

• Clinical data over several decades with valacyclovir and its metabolite, acyclovir, in pregnant women have not identified a drug-associated risk of major birth defects 1
• The Valacyclovir Pregnancy Registry documented outcomes of 111 infants exposed to valacyclovir during pregnancy with a 3.9% occurrence of major birth defects across all trimesters, which is comparable to the background risk in the general population (2-4%) 1
• A large population-based cohort study of 837,795 live births found no association between first-trimester exposure to valacyclovir and increased risk of major birth defects (adjusted POR 1.21; 95% CI 0.56-2.62) 2

Clinical Considerations for Use at 30 Weeks

When considering valacyclovir at 30 weeks:

1. Disease-associated risks:

   • Untreated genital herpes near delivery carries a 30-50% risk of neonatal HSV transmission 1
   • Recurrent genital herpes at term often necessitates cesarean delivery 3

2. Treatment benefits:

   • Valacyclovir suppression after 36 weeks significantly reduces HSV shedding and recurrent genital herpes requiring cesarean delivery (4% in valacyclovir group vs 13% in placebo group, P=0.009) 3
   • Valacyclovir provides higher plasma acyclovir levels than acyclovir therapy during late pregnancy 4

3. Pharmacokinetic considerations:

   • Valacyclovir is rapidly converted to acyclovir, which crosses the placenta
   • Acyclovir concentrates in amniotic fluid but shows no evidence of preferential fetal accumulation (maternal/umbilical vein plasma ratios at delivery were 1.7 for valacyclovir) 4

Recommendations for Use

• For first clinical episode of genital herpes during pregnancy, oral acyclovir treatment is appropriate 5
• For life-threatening maternal HSV infections (disseminated infection, encephalitis, pneumonitis, hepatitis), IV acyclovir is indicated 5
• For recurrent genital herpes near term, valacyclovir suppression can reduce the risk of cesarean delivery 3

Important Caveats

• The CDC guidelines note that routine administration of acyclovir/valacyclovir to pregnant women with a history of recurrent genital herpes was not recommended at the time of publication 5
• However, more recent evidence supports suppressive therapy near term to reduce cesarean deliveries 3
• At delivery, all women should be examined and questioned regarding symptoms of genital herpes 5
• Valacyclovir is well-tolerated in pregnancy with limited adverse effects reported 4

Monitoring Recommendations

If valacyclovir is prescribed at 30 weeks:

• Monitor for clinical signs of active lesions as delivery approaches
• Discuss the delivery plan based on presence/absence of active lesions at the time of labor
• Consider reporting the use to the pregnancy registry to improve the knowledge base on safety

In conclusion, while the decision to use valacyclovir at 30 weeks of pregnancy requires weighing benefits against potential risks, current evidence supports its safety when clinically indicated, particularly to prevent recurrent herpes outbreaks near delivery.