On ultrasound, a central placenta praevia is noted at 20 weeks in a woman with a previous lower-segment caesarean section. The single most important sonographic predictor of placenta accreta spectrum in this scenario is:

• A Subplacental venous lakes larger than 2 cm
• B Placental thickness greater than 5 cm
• C Loss of the normal hypoechoic retroplacental myometrial zone ✓
• D Anterior placenta with fundal predominance

Explanation

Loss of the normal hypoechoic retroplacental clear zone (representing myometrium) on grayscale ultrasound is the single most important sonographic sign of placenta accreta spectrum, reflecting absence of the normal decidua basalis and superficial myometrium. Vascular lacunae (Swiss-cheese appearance) add specificity but are a secondary sign. Placental thickness and position per se are not diagnostic.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.