A 28-year-old woman with 9 weeks of amenorrhea has a transvaginal ultrasound showing a gestational sac with an embryo whose crown-rump length measures 8 mm. Which additional finding establishes the diagnosis of pregnancy failure?
- A Absence of yolk sac
- B Mean sac diameter of 15 mm
- C Absence of cardiac activity ✓
- D Subchorionic hemorrhage
Correct answer: C. Absence of cardiac activity
Explanation
Once the crown-rump length reaches 7 mm or more, absence of embryonic cardiac activity is diagnostic of pregnancy failure. Absence of a yolk sac or subchorionic hemorrhage are equivocal findings requiring repeat scanning, and a mean sac diameter must reach 25 mm without an embryo before failure can be declared. These Society of Radiologists in Ultrasound thresholds prevent false labeling of an early normal pregnancy.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.