Varicella in Pregnancy — MD Dermatology Exam Notes

1. Introduction / Epidemiology

• Varicella (chickenpox) confers lifelong immunity; second attacks are rare in immunocompetent people.
• Women who reach child-bearing age without immunity have a small but definite risk of developing chickenpox in pregnancy: 0.05–0.07%.
• Incidence in pregnancy: 2–3/1000 pregnancies.
• Risk is gestational-age dependent:
  • Maternal risk of severe illness → greatest after mid-pregnancy (relative immunosuppression of pregnancy).
  • Fetal risk of congenital infection → greatest when maternal infection occurs in the 1st or 2nd trimester.

2. Maternal Complications

• Varicella is more severe in adults (>15 yrs) and infants (<1 yr) than in children, with higher rates of:
  • Pneumonia, hepatitis, encephalitis and higher mortality.
• Varicella pneumonia in pregnancy:
  • Occurs in 10–20% of pregnant women with chickenpox.
  • Severity increases with advancing gestation; highest risk in 3rd trimester.
  • Mortality ~14% in pregnant women vs 10–11% in general adult population.
• Risk factors for varicella pneumonitis in pregnancy:
  • 3rd trimester infection
  • Cigarette smoking
  • Chronic obstructive lung disease
  • Systemic steroid use in preceding 3 months / immunosuppression

  • 100 skin lesions or hemorrhagic lesions

3. Prevention of Maternal Varicella

• Determining immune status:
  • Non-immune = no past history of varicella/vaccine, or VZV IgG seronegative.
  • History of past chickenpox is 97–99% predictive of seropositivity.
• VZIG (Varicella Zoster Immunoglobulin):
  • Pooled plasma from high-titer donors; given as post-exposure prophylaxis to non-immune pregnant women.
  • Most effective within 72–96 hours of exposure (corresponds to immunoglobulin half-life).
  • No therapeutic benefit once rash has already developed.
• Aciclovir as prophylaxis: suggested by some authors, best given on day 7 post-exposure; prophylactic role not firmly established.
• Varicella vaccine (Varivax):
  • Live attenuated (Oka strain).
  • Contraindicated in pregnancy and in those planning pregnancy within 1 month.
  • Inadvertent vaccination in pregnancy is NOT an indication for termination.
  • Can be given pre-pregnancy (≥1 month before conception) or post-partum in seronegative women.

4. Management of Maternal Varicella Infection

• Fetal ultrasound 5 weeks after primary infection + follow-up recommended for 1st/2nd trimester maternal varicella (screen for fetal abnormalities).
• Isolation advice: avoid contact with other pregnant women/neonates during infectious period — from 1–2 days before rash onset until all lesions crust (~5 days after rash onset).
• Symptomatic care and hygiene to prevent secondary bacterial infection.

5. Fetal / Neonatal Complications

• Fetal (Congenital) Varicella Syndrome = embryopathy.
• Neonatal Varicella = actual chickenpox infection in first 10–12 days of life (no embryopathy).

A. Maternal varicella in 1st and 2nd trimester → Fetal Varicella Syndrome

• Develops in <2% of babies born to mothers infected between 7–28 weeks gestation.
• Mechanism: transplacental infection, but syndrome results from a subsequent in-utero herpes zoster reactivation, not the initial infection — occurs only in a minority of infected fetuses.
• Mortality: 30% in first month of life.
• Clinical features:
  • Low birth weight (LBW)
  • Cutaneous scars in dermatomal distribution
  • Papular lesions resembling connective tissue nevi
  • Ocular: cataract, microphthalmia, chorioretinitis
  • Bone and muscle hypoplasia (limb hypoplasia)
  • Neurological: mental retardation, seizures, hydrocephalus, cortical atrophy, microcephaly
  • Horner's syndrome, nystagmus
  • Bladder and bowel sphincter dysfunction

B. Maternal varicella in 3rd trimester

• Why this window is most dangerous: it coincides with the time needed for maternal IgG to form and cross the placenta — the neonate doesn't get adequate passive antibody, combined with relative immaturity of the neonatal immune system.
• Chickenpox appearing after this period in the neonate is more likely post-natally acquired.

Management of Neonatal Varicella

• VZIG immediately after birth if maternal rash onset is 5 days before to 2 days after delivery.
  • VZIG has reduced mortality in severe neonatal varicella from 31% to 7%.
• IV Aciclovir 10–15 mg/kg every 8 hours for 5–7 days, started within 24 hours of rash onset — reduces duration/severity.
• Delivery may be deliberately postponed (if in labor around the time of maternal rash) to allow maternal antibody transfer across placenta.
• No controlled trial yet proves efficacy of aciclovir/valaciclovir as post-exposure prophylaxis in neonates or pregnant women.

6. Quick Revision Table — Gestational Age vs Outcome

7. Key Exam Points to Remember

1. Fetal varicella syndrome is due to reactivation (zoster) in utero, not the primary infection itself — commonly asked distractor.
2. VZIG works only pre-eruption; useless once rash appears.
3. Varicella vaccine is a live vaccine → absolute contraindication in pregnancy, but accidental vaccination is not an indication for MTP.
4. The most dangerous period for the neonate is maternal rash 5 days before to 2 days after delivery — remember this exact window, it is frequently tested.
5. Aciclovir in pregnancy = Category B; oral for uncomplicated maternal disease, IV for pneumonitis or neonatal disease.
6. Classic triad-type features of congenital varicella syndrome: dermatomal cutaneous scarring + limb hypoplasia + CNS/eye anomalies.

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