Transvaginal ultrasound is performed to confirm suspected early pregnancy failure. Absence of embryonic cardiac activity is diagnostic of a failed pregnancy once the crown-rump length reaches at least:
- A 4 mm
- B 7 mm ✓
- C 12 mm
- D 20 mm
Correct answer: B. 7 mm
Explanation
The accepted sonographic threshold is absence of cardiac activity in an embryo with a crown-rump length of 7 mm or more, confirmed on transvaginal scanning. Below 7 mm, cardiac activity may simply be too early to detect and repeat scanning after an interval is advised. Similarly, a mean sac diameter of 25 mm or more without an embryo confirms failure. These cutoffs prevent erroneous diagnosis and iatrogenic interruption of a viable pregnancy.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.