Will a newborn contract herpes if the mother has an active herpes infection at the time of delivery?

Risk of Herpes Transmission from Mother to Newborn

A newborn has a significant risk of contracting herpes if the mother has an active herpes infection at delivery, with transmission rates of 30-50% for primary infections and 0-5% for recurrent infections, but cesarean delivery substantially reduces this risk. 1, 2

Transmission Risk Factors

The risk of neonatal HSV infection varies significantly based on several key factors:

• Type of maternal infection:

  • Primary (first episode) infection: 30-50% transmission risk 1
  • Recurrent infection: 0-5% transmission risk 1, 3

• Timing of maternal infection:

  • Highest risk when infection is acquired near delivery 1, 3
  • Lower risk with established infections 1

• Route of delivery:

  • Vaginal delivery with active lesions significantly increases risk 1, 3
  • Cesarean delivery reduces transmission by approximately 85% 3

• Other risk factors:

  • Prolonged rupture of membranes (>6 hours) 1
  • Use of invasive procedures (e.g., fetal scalp monitoring) 1, 3
  • HSV-1 vs HSV-2 (HSV-1 has higher transmission risk) 3
  • Maternal age <21 years 3
  • Delivery before 38 weeks 3

Prevention Strategies

To prevent neonatal herpes infection when a mother has active herpes:

1. Cesarean delivery:

   • Recommended for women with active genital lesions or prodromal symptoms at onset of labor 1, 2
   • Significantly reduces transmission risk from 7.7% to 1.2% when HSV is present 3

2. Antiviral therapy:

   • For primary infections during pregnancy: Acyclovir 400 mg three times daily for 7-10 days 2
   • Suppressive therapy starting at 36 weeks' gestation for women with history of genital herpes:
     • Valacyclovir 500 mg twice daily OR
     • Acyclovir 400 mg three times daily 2
   • Reduces viral shedding, recurrences, and need for cesarean deliveries 2

3. Preventive measures during pregnancy:

   • Avoid unprotected genital and oral sexual contact during late pregnancy 1, 2
   • Proper hand hygiene and avoiding direct contact with lesions 2

Neonatal Management

If a newborn is exposed to maternal HSV:

• Immediate evaluation and treatment with IV acyclovir (20 mg/kg/dose three times daily) 2
• Diagnostic workup including surface cultures/PCR, blood HSV PCR, CSF HSV PCR, and liver function tests 2
• Treatment duration depends on disease classification:
  • Skin, Eye, Mouth (SEM) disease: 14 days 2
  • CNS or disseminated disease: 21 days 2

Important Caveats

• Asymptomatic shedding: Even without visible lesions, HSV can be transmitted to the newborn 1
• Congenital HSV: In-utero acquisition is rare but can cause devastating damage 1
• HIV coinfection: Women with HIV/HSV coinfection have higher rates of HSV shedding (10% vs 2-3%) 1
• Breastfeeding: Generally safe unless mother has cracked nipples with detectable HSV DNA 2

Despite preventive measures, neonatal HSV can still occur. Early recognition and prompt treatment are essential to reduce morbidity and mortality in affected infants.