Placenta circumvallata is a structural abnormality of the placenta in which the chorionic plate is smaller than the basal plate, leading to folding back of the placental and fetal membranes. It is associated with numerous prenatal and perinatal complications, including placental abruption, preterm delivery, fetal malformations, growth restriction, and perinatal death in rare cases. The diagnosis can be made by standard ultrasonography during the second or third trimester.
The development of placenta circumvallata carries a significant risk for the development of complications during pregnancy. These complications carry a poor prognosis and include ascending infection and consequent chorioamnionitis due to formation of a hematoma, or oligohydramnios , while placental abruption, preterm delivery, and emergency cesarean section have also been reported in women suffering from this condition  . Additionally, the abnormality of the placenta impairs normal nutrient delivery (placental hypoplasia, deposition of hemosiderin and infarcts are suspected mechanisms of disease), which is why intrauterine growth restriction, fetal malformations, and even perinatal death was observed in some cases . Persistent vaginal bleeding is one of the most prominent clinical manifestations of placenta circumvallata and is usually present during the first and second trimesters , but other authors claim that bleeding may be present during the 3rd trimester as well . Women who eventually had a preterm delivery were more likely experiencing bleeding episodes, predominantly during the second semester, whereas intrauterine growth abnormalities (IUGR) and a small weight and/or height for gestational age were significantly linked with hemorrhage during the third semester . Premature rupture of the membranes (PROM) and chronic fetal lung disease (CLD) may also be induced by this placental abnormality  .
The first step in the diagnostic workup is obtaining a detailed patient history that will identify the onset and frequency of symptoms, and their features should immediately point to a fetal-related disorder. The majority of pregnancies in whom placenta circumvallata develops, unfortunately, receive a diagnosis after gross examination of this organ following delivery or termination of pregnancy . Nevertheless, persistent bleeding during pregnancy, miscarriage or development of complications without an identifiable cause must raise suspicion regarding placental abnormalities, and a meticulous examination must be performed, since placenta circumvallata may be difficult to visualize. A rounded placental margin with an irregular, uplifted edge is one of the typical signs detected using standard ultrasonography, but measurement of placental thickness may also be highly useful  . Unfortunately, the accuracy of ultrasonography is quite limited when it comes to detecting this placental disorder, as certain reports show a very low rate of diagnosis . The introduction of more advanced imaging studies, however, such as HD live and live silhouette mode imaging, has shown promising results and their use in clinical practice might be of significant benefit . A central placental depression with very thick folded edges that form the irregular placental margins (which are the hallmark of the condition) may be visualized by this procedure, making it highly useful if the diagnosis remains uncertain .