What is the recommended management for a 35-week pregnant woman with Herpes Simplex Virus (HSV) infection?

Management of HSV at 35 Weeks Gestation

For a pregnant woman at 35 weeks with HSV, initiate suppressive antiviral therapy immediately with either acyclovir 400 mg three times daily or valacyclovir 500 mg twice daily, continuing until delivery to reduce clinical recurrences, viral shedding, and the need for cesarean delivery. 1, 2

Immediate Antiviral Suppression

The management approach differs critically based on whether this represents a first episode versus a recurrence:

First Episode During Pregnancy

• Start treatment immediately with acyclovir 400 mg orally three times daily for 7-10 days OR valacyclovir 1 g orally twice daily for 7-10 days 1
• After completing the acute treatment course, transition to suppressive therapy from 36 weeks until delivery: acyclovir 400 mg three times daily 1, 3
• The risk of neonatal transmission is 25-44% if a first episode is ongoing at delivery, making aggressive management essential 4
• Cesarean delivery is recommended if the first episode occurred less than 6 weeks before delivery or if active lesions are present at labor onset 4

Recurrent HSV During Pregnancy

• Begin suppressive prophylaxis at 36 weeks (which is now, at 35 weeks): acyclovir 400 mg three times daily OR valacyclovir 500 mg twice daily 1, 5, 6
• This reduces clinical recurrences at delivery by 75% (OR 0.25) and cesarean deliveries for HSV by 70% (OR 0.30) 5
• The neonatal transmission risk with recurrent HSV at delivery is only 1-3%, substantially lower than primary infection 1, 4

Safety Profile in Late Pregnancy

Acyclovir and valacyclovir are safe at 35 weeks gestation:

• Current registry data show no increased risk of major birth defects compared to the general population (3.2% for acyclovir, 4.5% for valacyclovir versus 2-4% background risk) 7
• Acyclovir remains FDA pregnancy category B 8
• No neonatal adverse effects have been documented in multiple trials 3, 6
• One caveat: A case-control study showed increased odds of gastroschisis with antiherpes medication use between one month pre-conception and the third month of pregnancy, but this does not apply to third-trimester use 8

Delivery Planning

Examine carefully for lesions or prodromal symptoms at labor onset:

• Cesarean delivery is indicated if active genital lesions or prodromal symptoms are present at the time of labor 1
• For recurrent HSV with intact membranes and active lesions at labor, cesarean is recommended 4
• Vaginal delivery is acceptable if no clinical lesions are present and membranes have been ruptured for a prolonged period with recurrent HSV 4
• Most mothers of infants who acquire neonatal herpes lack histories of clinically evident genital herpes, emphasizing the importance of careful examination 1

Monitoring and Counseling

Key counseling points to address now:

• Explain that the risk of neonatal infection varies dramatically: 30-50% for acquisition near delivery versus ≤3% for recurrent herpes at term 1
• Advise strict avoidance of unprotected genital and oral sexual contact during late pregnancy, especially with partners who have oral or genital HSV 1
• Ensure she informs all healthcare providers caring for her during delivery about the HSV infection 1
• No routine viral cultures are needed at delivery unless lesions are present 4

Breastfeeding Guidance

Breastfeeding is safe and should not be discouraged after delivery, as there is no evidence of HSV transmission through breast milk 7

• A maternal dose of valacyclovir 500 mg twice daily would provide a breastfed infant with approximately 0.6 mg/kg/day of acyclovir, which is considered safe 7

Common Pitfall to Avoid

Do not wait until 36 weeks to start suppressive therapy if the patient is already at 35 weeks—begin immediately to maximize the protective effect against viral shedding and recurrence at delivery 5, 6. The evidence supporting suppressive therapy from 36 weeks means "starting at 36 weeks," not delaying treatment if the patient presents at 35 weeks.