Placental shelf

A placental shelf refers to a ridge of placental tissue freely abutting the margin. It may represent part of a circumvallate placenta, although an early second-trimester placental shelf can be a common, benign and transient finding.

Placental shelves detected in early second-trimester are thought to rarely persist to mid-gestation and never to the third trimester.

Radiographic features

Ultrasound

Typically seen as a peripheral uplifted rim of chorionic tissue appearing as an echodense ridge.