**Core Concept**
Circumvallate placenta refers to a rare type of placental anomaly characterized by a ring of placental tissue surrounding a central area of chorionic plate, resulting from an incomplete fusion of the chorionic villi during embryogenesis. This condition can lead to placental insufficiency and increased maternal and fetal morbidity.

**Why the Correct Answer is Right**
In a circumvallate placenta, the chorionic plate is larger than the basal plate, resulting in a central depression and a ring-like appearance. This anomaly is thought to occur due to an incomplete fusion of the chorionic villi during embryonic development. The condition can lead to increased risk of placental abruption, fetal growth restriction, and preterm labor.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because circumvallate placenta is not associated with an increased risk of placenta accreta. While both conditions are placental anomalies, they have distinct pathophysiologies.
**Option B:** Incorrect because circumvallate placenta is not a type of marginal placenta. Marginal placenta refers to a placenta that is attached to the side of the uterus, whereas circumvallate placenta is a distinct type of placental anomaly.
**Option C:** Incorrect because circumvallate placenta is not a type of placenta previa. Placenta previa refers to a condition where the placenta covers the cervical os, whereas circumvallate placenta is a distinct type of placental anomaly.

**Clinical Pearl / High-Yield Fact**
Circumvallate placenta is a rare but significant placental anomaly that can lead to increased maternal and fetal morbidity. It is essential for obstetricians and sonologists to recognize this condition and manage it appropriately to prevent complications.

**Correct Answer:** D.