A 35-year-old woman with a previous classical cesarean section presents at 32 weeks with painless bright red vaginal bleeding. Ultrasound shows placenta previa with the placenta directly overlying the previous uterine scar. The MOST critical additional sonographic feature to assess, given the scar site, is:

• A Placental lakes and retroplacental clear space loss to diagnose accreta spectrum ✓
• B Cervical length to predict timing of significant hemorrhage
• C Placental cord insertion site to assess for velamentous vessels
• D Uterine artery Doppler to assess uteroplacental circulation

Explanation

When placenta previa overlies a prior uterine scar (especially classical cesarean), placenta accreta spectrum (PAS) is the critical diagnosis to exclude. Sonographic markers of PAS include: loss of the normal retroplacental clear space (hypoechoic zone), presence of placental lacunae (Swiss cheese appearance), bladder wall irregularity/bulging, and bridging vessels crossing the placenta-bladder interface on Doppler. These features have highest diagnostic significance in this context. Cervical length (B) predicts preterm labor risk but not accreta. Cord insertion (C) evaluates for vasa previa, a different condition. Uterine artery Doppler (D) assesses perfusion, not accreta anatomy.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.