How should a 33‑week pregnant woman with a known history of genital herpes simplex virus infection and no active lesions be managed to prevent maternal outbreak and neonatal HSV infection?

Management of Pregnant Woman at 33 Weeks with History of HSV and No Active Lesions

Start suppressive antiviral prophylaxis at 36 weeks gestation with either acyclovir 400 mg orally three times daily or valacyclovir 500 mg orally twice daily, continuing until delivery. 1, 2

Current Management at 33 Weeks

No Immediate Intervention Required

• At 33 weeks gestation with no active lesions, no antiviral treatment is indicated at this time—suppressive therapy should be initiated at 36 weeks gestation. 1, 2
• Continue routine prenatal care and monitor for any signs of HSV recurrence (prodromal symptoms, visible lesions). 3

Patient Counseling Now

• Inform the patient that the risk of neonatal transmission with recurrent HSV at delivery is low (1–3%), compared to 30–50% with primary infection near term. 1, 2
• Explain that suppressive therapy starting at 36 weeks reduces clinical recurrences at delivery from 27–36% to 5–11% and decreases cesarean delivery rates by approximately 60–70%. 1
• Advise abstaining from sexual activity if any lesions develop and avoiding oral-genital contact if either partner has oral herpes. 3, 4

Suppressive Prophylaxis Protocol Starting at 36 Weeks

Medication Regimens

• Preferred option: Acyclovir 400 mg orally three times daily from 36 weeks until delivery. 1, 2
• Alternative option: Valacyclovir 500 mg orally twice daily from 36 weeks until delivery (some sources recommend valacyclovir 1000 mg twice daily). 1, 2
• Both medications are pregnancy category B with decades of safety data showing no pattern of adverse pregnancy outcomes or major congenital anomalies. 1, 5

Safety Considerations

• Clinical data over several decades demonstrate no increased risk of major birth defects with acyclovir or valacyclovir use in pregnancy compared to the general population (2–4% baseline risk). 5
• One case-control study found increased odds of gastroschisis (OR 4.7) with periconceptional use (one month before through three months after conception), but this had significant confounders and recall bias. 1
• Initiating therapy at 36 weeks avoids first-trimester exposure while maximizing prevention of neonatal transmission. 1

Delivery Management Algorithm

If No Lesions Present at Labor Onset

• Proceed with vaginal delivery if no visible genital lesions or prodromal symptoms are present at the time of labor. 1, 2
• Avoid invasive fetal monitoring (fetal scalp electrodes, intrauterine pressure catheters) unless there are clear obstetric indications, as these increase neonatal transmission risk. 6, 7

If Lesions or Prodrome Present at Labor Onset

• Immediate cesarean delivery is mandatory if visible genital lesions or prodromal symptoms (tingling, burning, itching) are present at labor onset, regardless of whether this represents primary or recurrent disease. 1, 2
• Cesarean delivery reduces transmission risk by approximately 85% when HSV is being shed at delivery. 1, 7
• Do not rely on antiviral medication alone when active lesions are present—cesarean section is the standard of care. 1

Common Pitfall to Avoid

• Prenatal viral cultures obtained during pregnancy should NOT be used to guide delivery management, as they do not predict viral shedding at the time of delivery and are not cost-effective. 1, 8

Neonatal Management After Delivery

Surveillance for All Exposed Infants

• All newborns with maternal HSV exposure should have surveillance cultures obtained from the conjunctiva, oral cavity, nasopharynx, and rectum at 24–48 hours after birth (not immediately at delivery, as this may reflect maternal contamination). 1
• Cultures obtained at 24–48 hours provide the most reliable information for detecting neonatal HSV before clinical signs appear. 1

Low-Risk Scenario (Your Patient)

• For infants born to mothers with recurrent HSV on suppressive therapy and no lesions at delivery, routine empiric acyclovir is NOT recommended if the infant is asymptomatic. 1
• Observe the infant clinically and await surveillance culture results. 1

When to Treat the Neonate

• Start IV acyclovir 20 mg/kg three times daily immediately if the infant develops skin vesicles, has positive surveillance cultures, or shows any signs of infection. 1
• High-risk infants (maternal primary infection in the last month of pregnancy) may warrant empiric acyclovir even if asymptomatic—consult pediatric infectious disease. 1

Key Risk Stratification

Your Patient's Risk Profile

• History of recurrent HSV with no active lesions during current pregnancy represents low risk for neonatal transmission. 1, 2
• With suppressive therapy starting at 36 weeks and no lesions at delivery, the transmission risk is approximately 1–3%. 1, 2

Highest Risk Scenario (Not Your Patient)

• Primary or first-episode HSV infection in the third trimester carries a 30–50% neonatal transmission risk, even with cesarean delivery. 1, 5
• These cases may warrant empiric neonatal acyclovir therapy and require pediatric infectious disease consultation. 1