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Varicella exposure in pregnancy — MSRA MCQ

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ModerateInfectious DiseasesVaricella exposure in pregnancyMSRA

A 30-year-old woman who is 24 weeks pregnant contacts her GP. Her 4-year-old daughter developed a typical vesicular rash 7 days ago and has been diagnosed clinically with chickenpox. They live together and the woman provided close care throughout the daughter’s prodrome and rash. The woman has no history of chickenpox or shingles and has not received varicella vaccine. An urgent VZV IgG result taken yesterday is 62 mIU/mL. She is well, can take oral medication, has an eGFR of 94 mL/min/1.73 m² and takes only folic acid. What is the most appropriate management today?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Start oral aciclovir 800 mg four times daily for 7 days today

Explanation lettering: E = shown as A · A = shown as B · B = shown as C · C = shown as D · D = shown as E

This is a significant household exposure to varicella in a pregnant woman without evidence of immunity. For household contacts, the exposure day is defined as the day of onset of the index case’s rash. Her VZV IgG concentration of 62 mIU/mL confirms susceptibility using the UKHSA threshold of less than 100 mIU/mL for pregnant contacts. She is therefore eligible for post-exposure prophylaxis. Today is day 7 after exposure, which is the appropriate time to begin antiviral prophylaxis. UKHSA recommends oral aciclovir 800 mg four times daily for 7 days for susceptible pregnant women. Oral valaciclovir is an alternative, but is not offered here. A is inappropriate because intravenous varicella immunoglobulin is reserved for exceptional circumstances where oral antivirals cannot be used, such as malabsorption or relevant renal toxicity. B uses the therapeutic chickenpox regimen, which is indicated if she develops chickenpox, rather than prophylaxis. C fails to reduce the risk or severity of maternal varicella after a confirmed significant exposure in a susceptible pregnant contact. D is contraindicated because live attenuated varicella vaccine must not be given during pregnancy.

Reference: UKHSA: Guidelines on post-exposure prophylaxis (PEP) for varicella or shingles (Updated 19 March 2026) — https://www.gov.uk/government/publications/post-exposure-prophylaxis-for-chickenpox-and-shingles/guidelines-on-post-exposure-prophylaxis-pep-for-varicella-or-shingles-january-2023 UKHSA: Guidelines on post-exposure prophylaxis (PEP) for varicella or shingles (Updated 19 March 2026) — https://www.gov.uk/government/publications/post-exposure-prophylaxis-for-chickenpox-and-shingles/guidelines-on-post-exposure-prophylaxis-pep-for-varicella-or-shingles-january-2023