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Pregnancy of unknown location — DFSRH MCQ

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EasyDifferential DiagnosisPregnancy of unknown locationDFSRH

A 31-year-old woman attends an early pregnancy service with 3 days of light vaginal bleeding and intermittent left iliac fossa pain. A 52 mg levonorgestrel intrauterine device was inserted 18 months ago and remains in date. Her urine pregnancy test is positive. She is haemodynamically stable, with mild left iliac fossa tenderness but no guarding or cervical motion tenderness. Transvaginal ultrasonography shows the intrauterine device correctly positioned at the fundus. No intrauterine gestational sac, adnexal mass or significant free fluid is seen. Serum human chorionic gonadotrophin is 980 IU/L and rises to 1210 IU/L 48 hours later. Which diagnosis best describes the pregnancy at this assessment?

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Correct answer: C — Pregnancy of unknown location

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

This is a pregnancy of unknown location: pregnancy is biochemically confirmed, but transvaginal ultrasonography identifies neither an intrauterine nor an extrauterine pregnancy. The suboptimal 48-hour hCG rise increases concern for a non-viable or ectopic pregnancy and requires prompt early-pregnancy review, but hCG measurements must not be used to determine pregnancy location. Pregnancy occurring with intrauterine contraception in situ has a higher proportional likelihood of being ectopic than pregnancy occurring without intrauterine contraception. This makes exclusion of ectopic pregnancy particularly important, but it does not establish that diagnosis without diagnostic imaging or operative findings. A is incorrect because no intrauterine pregnancy has been visualised and viability cannot be inferred from hCG alone. B requires an identified intrauterine gestational sac whose viability remains uncertain. C cannot be diagnosed solely from bleeding and an empty uterus when no previous scan confirmed an intrauterine pregnancy; such a presentation must remain classified as pregnancy of unknown location pending follow-up. D is an important differential diagnosis, especially given the pain, intrauterine device and abnormal hCG trend, but no adnexal pregnancy or other definitive ectopic finding has been demonstrated.

Reference: FSRH Guideline: Intrauterine Contraception (March 2023, amended July 2023) — https://www.fsrh.org/Common/Uploaded%20files/documents/fsrh-clinical-guideline-intrauterine-contraception-mar-23-amended.pdf Ectopic pregnancy and miscarriage: diagnosis and initial management — Diagnosis of viable intrauterine pregnancy and tubal ectopic pregnancy (17 June 2026) — https://www.nice.org.uk/guidance/NG126/chapter/diagnosis-of-viable-intrauterine-pregnancy-and-of-tubal-ectopic-pregnancy