What is the recommended Herpes Simplex Virus (HSV) prophylaxis treatment for a 35-week pregnant individual?

HSV Prophylaxis at 35 Weeks Gestation

Primary Recommendation

For pregnant women at 35 weeks gestation with a history of genital herpes during pregnancy, initiate suppressive antiviral prophylaxis with oral acyclovir 400 mg three times daily (or valacyclovir 1000 mg twice daily) starting at 36 weeks and continuing until delivery. 1, 2, 3

Clinical Decision Algorithm

Step 1: Determine HSV History Status

Women with documented genital herpes during current pregnancy:

• Start suppressive therapy at 36 weeks gestation with acyclovir 400 mg orally three times daily OR valacyclovir 1000 mg orally twice daily 1, 2, 4
• This applies to both first episode and recurrent genital herpes during pregnancy 4, 5

Women with history of genital herpes but NO recurrence during current pregnancy:

• Routine prophylaxis is NOT recommended by current guidelines 4
• However, some experts recommend prophylaxis for women with frequent, severe recurrences (BIII recommendation) 6

Step 2: Expected Benefits of Prophylaxis

The evidence strongly supports that suppressive therapy from 36 weeks reduces:

• Clinical HSV recurrences at delivery by 75% (RR 0.25,95% CI 0.15-0.40) 3, 7
• Cesarean deliveries for genital herpes by 70% (RR 0.30,95% CI 0.20-0.45) 3, 7
• HSV viral shedding at delivery by 86% (RR 0.14,95% CI 0.05-0.39) 3, 7
• Clinical recurrence rates drop from 18-37% in historical controls to only 1-4% with suppression 5

Safety Profile in Pregnancy

Acyclovir and valacyclovir are safe for use in late pregnancy:

• Clinical data over several decades show no increased risk of major birth defects compared to the general population 8
• The Acyclovir Pregnancy Registry documented 1,246 exposures with a 3.2% rate of major birth defects during first-trimester exposure (within background risk) 8
• No pattern of adverse pregnancy outcomes has been reported 6
• Current FDA labeling confirms no drug-associated risk of major birth defects based on extensive clinical experience 8

Dosing Regimens

Preferred options for suppressive prophylaxis starting at 36 weeks:

• Acyclovir 400 mg orally three times daily until delivery 1, 2, 4, 5
• Valacyclovir 1000 mg orally twice daily until delivery (alternative with better compliance due to twice-daily dosing) 2, 4

Critical Context: Neonatal Transmission Risk

Understanding transmission risk guides the urgency of prophylaxis:

• Primary HSV infection near delivery: 30-50% neonatal transmission risk 1, 2, 8, 4
• Recurrent HSV at delivery: 1-3% neonatal transmission risk 1, 2, 4
• Most mothers of infants with neonatal herpes lack histories of clinically evident genital herpes 2
• The risk of HSV seroconversion during pregnancy is 1-5% 4

Management at Delivery (35 Weeks Context)

If labor begins at 35 weeks with active lesions:

• Cesarean delivery is mandatory if visible genital lesions or prodromal symptoms are present at labor onset, regardless of whether this represents primary or recurrent disease 1, 2, 4
• Acyclovir given at the time of labor does NOT adequately prevent neonatal transmission when active lesions are present 1
• Cesarean delivery reduces transmission risk by approximately 85% when lesions are present 1

If first episode occurred less than 6 weeks before delivery:

• Cesarean delivery is recommended even without visible lesions at labor onset 4

Common Pitfalls to Avoid

• Do not delay prophylaxis beyond 36 weeks - the evidence base specifically supports initiation at 36 weeks gestation 1, 3, 7
• Do not rely on antiviral therapy alone if lesions are present at delivery - cesarean section remains the standard of care 1
• Do not assume all pregnant women with HSV need prophylaxis - only those with documented infection during the current pregnancy have clear indication 4
• Do not use topical antivirals - systemic oral therapy is required for suppression 6

Patient Compliance Considerations

• In clinical practice, 85% of patients are compliant with three-times-daily acyclovir suppression 5
• Valacyclovir's twice-daily dosing may improve compliance compared to acyclovir's three-times-daily regimen 9, 4
• The therapy is cost-effective when considering reduced cesarean delivery rates 9

Neonatal Monitoring After Delivery

All infants exposed to HSV during birth require:

• Careful clinical follow-up with surveillance cultures of mucosal surfaces 24-48 hours after birth 1
• Do NOT routinely treat asymptomatic exposed infants with acyclovir 1
• Infants born to women with primary infection near term are high-risk; some experts recommend empiric acyclovir therapy 1
• Any infant with evidence of neonatal herpes should receive IV acyclovir 20 mg/kg three times daily immediately 1, 4