A woman with 10 weeks of amenorrhoea has a transvaginal ultrasound showing an intrauterine gestational sac with no embryo visualised. Which finding establishes the diagnosis of failed early pregnancy?
- A Mean sac diameter of 16 mm or more with no embryo
- B Mean sac diameter of 25 mm or more with no embryo ✓
- C Yolk sac larger than 6 mm
- D Absence of cardiac activity on a single scan at 10 weeks
Correct answer: B. Mean sac diameter of 25 mm or more with no embryo
Explanation
Diagnostic criteria for early pregnancy failure on transvaginal scanning are a crown-rump length of 7 mm or more with no cardiac activity, or a mean sac diameter of 25 mm or more with no embryo. These thresholds come from a multicentre prospective study and are endorsed by ACOG and Williams Obstetrics. B mean sac diameter of 16 mm or more without an embryo is classified as suspicious rather than diagnostic, and such cases require a repeat scan after 7 to 14 days before failure is declared.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.