Circumvallate placenta is a placental disease in which the fetal membranes (chorion and amnion) "double back" on the fetal side around the edge of the placenta.[1] After delivery, a circumvallate placenta has a thick ring of membranes on its fetal surface.[2]
Complete circumvallate placenta occurs in approximately 1% of pregnancies.[1] It is diagnosed prenatally by medical ultrasonography, although one 1997 study of prenatal ultrasounds found that "of the normal placentas, 35% were graded as probably or definitely circumvallate by at least one sonologist," and "all sonologists misgraded the case of complete circumvallation as normal."[1] The condition is associated with perinatal complications such as placental abruption, oligohydramnios, abnormal cardiotocography, preterm birth, and miscarriage.[3]
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