Circumvallate placenta

Last revised by Jeremy Jones on 20 Sep 2021

Circumvallate placenta refers to a variation in placental morphology in which, as a result of a small chorionic plate, the amnion and chorion fetal membranes ‘double back’ around the edge of the placenta.

The prevalence is estimated to be around 1-7% 3.

There is an inward insertion of membranes from the edge towards the center of the placenta (from deep implantation of the placenta into the decidua). Because of this excessive implantation, the placenta covers more than half of the fetal sac. The placenta reduces this excessive covering to the normal one-fourth by separating from the uterine wall, with the resultant back folding of the placenta and fetal membranes towards the chorionic surface.

This can be accompanied by tethering of membranes, frequently in association with a marginal infarction, hemorrhage, or fibrin deposition. 

May show a peripheral rim of chorionic tissue appearing as an echodense ridge (placental shelf2,6.

On 3D ultrasound, it has an appearance similar to a tire (the "tire sign").

Recognized complications include 1,4:

For a raised placental edge on ultrasound:

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Cases and figures

  • Figure 1: diagram - circumvallate placenta
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  • Case 1
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  • Case 2
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  • Case 3
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