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Assessment of rubella protection before pregnancy — DFSRH MCQ

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EasySerologyAssessment of rubella protection before pregnancyDFSRH

A 31-year-old woman attends a sexual and reproductive health clinic before attempting conception. A private fertility assessment has reported that rubella IgG was not detected. Her NHS record documents two MMR doses, administered at 14 months and 4 years of age. She is immunocompetent, is not pregnant and currently uses a progestogen-only pill, which she wishes to stop today. She asks whether the negative serology means that pregnancy should be deferred. Which is the most appropriate advice?

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

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Correct answer: C — Regard the documented two-dose history as evidence of protection and allow her to stop contraception without further testing

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

The documented administration of two appropriately timed MMR doses is sufficient evidence of rubella protection. UKHSA advises that women planning pregnancy should have two documented doses of rubella-containing vaccine; there is no requirement for rubella IgG testing or for the measured concentration to exceed 10 IU/mL. Routine assays may fail to detect low-level vaccine-induced antibody despite clinically adequate protection. She therefore need not defer conception or undergo repeat serology. A is a plausible response to negative serology because UKHSA permits an optional third MMR dose for reassurance after inadvertent testing. It is not required, however, and the recommended pregnancy-avoidance interval after MMR is 1 month, not 3 months. B applies when two valid doses have not already been documented. D incorrectly treats detectable antibody as the required endpoint and may perpetuate misleading testing. E is inappropriate because MMR is a live attenuated vaccine and is contraindicated during pregnancy; an incompletely vaccinated pregnant patient would instead be offered missing doses postpartum.

Reference: Immunisation against infectious disease: Rubella chapter (14 April 2026) — https://assets.publishing.service.gov.uk/media/69dceebddaa863aa5db66628/UKHSA_Green_Book_chapter_Rubella_7_4_26__002_.pdf Vaccine update: issue 368, January 2026, maternity special (January 2026) — https://www.gov.uk/government/publications/vaccine-update-issue-368-january-2026-maternity-special/vaccine-update-issue-368-january-2026-maternity-special