* Fetal medicine unit, Cairo University, Egypt;

** Radiology department, Kasr Alainy teaching hospitals, Cairo University, Egypt.

Fusion of fetal amniotic membranes medially in relation to the chorionic plate true edge leads to the formation of a placental shelf which should put circumvallate placenta in the differential diagnosis¹. This will lead to elevated or rolled-up placental edge. This placental shelf should not attach to any part of the fetus and should have a free edge projecting into the uterine cavity ^2,3. In cases of circumvallate placenta, this shelf may be only apparent in second trimester but not in the third trimester when only a bright border at the edge of the placenta may be noticed3. Sub-amniotic anechoic areas are seen in some cases of circumvallate placenta³ and according to some authors, they represent an important clue to the diagnosis⁴. There is ongoing debate about the significance of the circumvallate placenta; some refer to it as an anatomic variant⁴ however recently some reports of increased risk of adverse outcome have been published⁵.

Case report 

A 29 year old pregnant woman presented to us at 23 weeks gestation for routine ultrasound study. Our ultrasound examination revealed the presence of circumvallate placenta.


Images 1-6 and Videos 1, 2: show the discrepancy between the basal and the chorionic plates, the rolled-up placenta edges (shelf) and the marginal sub-amniotic anechoic areas.