Fetal Varicella Syndrome — SCE Infectious Diseases MCQ

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ModerateTravel Medicine & VaccinationFetal Varicella SyndromeSCE Infectious Diseases

A 25-year-old pregnant woman (12 weeks) develops primary chickenpox (confirmed by VZV IgM and clinical vesicular rash). She has no complications. At what gestational age is the risk of fetal varicella syndrome (FVS) highest?

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Correct answer: A — Before 20 weeks gestation (risk approximately 1–2%)

Fetal varicella syndrome (FVS) occurs when maternal primary varicella in the first 20 weeks of pregnancy causes in utero fetal infection. The risk is approximately 0.4% at 0–12 weeks and 2% at 13–20 weeks. After 20 weeks, the risk of FVS is negligible. FVS features include skin scarring, limb hypoplasia, eye defects, and neurological abnormalities. Detailed fetal ultrasound at 5 weeks post-infection and at 16–20 weeks is recommended. Maternal VZV in the peripartum period (5 days before to 2 days after delivery) causes neonatal varicella, which is a separate, serious risk.

Reference: UKHSA 2024 – Green Book Ch 34: Varicella; RCOG 2015 – Chickenpox in pregnancy