Can a pregnant woman have herpes simplex virus type 2 (HSV-2) without it showing up in a lab test?

Herpes Simplex Virus Type 2 (HSV-2) in Pregnancy: Detection and Management

Yes, it is possible for a pregnant woman to have herpes simplex virus type 2 (HSV-2) infection without it showing up in a lab test. This occurs due to limitations in testing sensitivity and the nature of viral shedding patterns 1.

Why HSV-2 May Not Be Detected During Pregnancy

• Intermittent viral shedding: HSV-2 can remain dormant in nerve ganglia and shed intermittently, meaning the virus may not be actively replicating at the time of testing 1
• Test limitations: No test is 100% sensitive, and false negatives can occur
• Timing of infection: Recently acquired infections may not have produced sufficient antibodies for detection
• Asymptomatic infections: Up to 80% of HSV-2 infections are asymptomatic, making clinical diagnosis challenging 1

Testing Considerations During Pregnancy

• Type-specific serologic tests are recommended for diagnosing HSV-2 in pregnancy when clinical symptoms are present 1
• Routine screening for HSV serostatus during pregnancy is not recommended by the American College of Obstetrics and Gynecology due to lack of evidence for cost-effectiveness 1, 2
• Viral cultures during pregnancy do not reliably predict viral shedding at delivery and are not indicated routinely 1

Risks of HSV-2 in Pregnancy

• Neonatal transmission risk is highest (30-50%) when a mother acquires genital herpes near the time of delivery 1
• Risk is lower (approximately 3%) among women with recurrent herpes at term or who acquire HSV during the first half of pregnancy 1
• Maternal genital herpes is a risk factor for perinatal mother-to-child HIV transmission in HIV-positive women 1

Management Recommendations

For Women with Known HSV-2 Infection:

1. Suppressive therapy with acyclovir (400 mg TID) or valacyclovir (500 mg BID) starting at 36 weeks' gestation reduces:

   • Viral shedding
   • Recurrences
   • Need for cesarean deliveries 1

2. Cesarean delivery is recommended for women with:

   • Genital herpes prodrome
   • Visible HSV genital lesions at the onset of labor 1

3. Acyclovir is the antiviral drug with the most reported experience in pregnancy and appears to be safe; therefore, it is the first choice for therapy of HSV infections in pregnancy 1

For Women with Suspected New HSV-2 Infection:

• Immediate testing with type-specific serologic tests and viral culture if lesions are present
• Counseling about the high risk of transmission if infection occurs in late pregnancy
• Avoidance of unprotected genital and oral sexual contact during late pregnancy, especially for susceptible women 1

Important Considerations

• Breastfeeding should not be discouraged in HSV-infected mothers unless they have cracked nipples and detectable HSV DNA 1
• Invasive fetal monitoring can increase the risk of neonatal herpes and should only be used for defined obstetrical indications 3
• Safety of antivirals: Acyclovir has been extensively studied in pregnancy with no increased risk of major birth defects compared to the general population 1, 4

Prevention of Neonatal Herpes

• Examine all women at the onset of labor for symptoms of genital herpes
• Cesarean delivery significantly reduces HSV transmission rates among women with active HSV infection (1.2% vs 7.7% with vaginal delivery) 5
• Avoid triggers that may cause recurrence near term (stress, UV radiation, local trauma) 4

Remember that the highest risk of neonatal infection occurs when the mother acquires genital HSV in the third trimester, making prevention of new infections during pregnancy a critical goal 3.