A woman with 7 weeks of amenorrhea and light bleeding undergoes transvaginal ultrasound. There is an intrauterine gestational sac with a mean diameter of 18 mm containing a yolk sac but no embryo, and no cardiac activity is seen. What is the correct next step?
- A Repeat transvaginal scan in 7 to 14 days before any diagnosis of failure ✓
- B Diagnose missed abortion and arrange evacuation
- C Start mifepristone and misoprostol immediately
- D Measure serum beta-hCG and terminate based on the value
Correct answer: A. Repeat transvaginal scan in 7 to 14 days before any diagnosis of failure
Explanation
The strict criteria for diagnosing a failed pregnancy are a mean sac diameter of 25 mm or more without an embryo, or a crown-rump length of 7 mm or more without cardiac activity. An 18 mm sac without an embryo falls short of these thresholds, so the pregnancy is indeterminate and a repeat scan in 7 to 14 days is mandatory. Acting on a single subthreshold scan risks evacuating a normal early pregnancy, and a single hCG value cannot distinguish viable from failed gestation reliably.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.