Common Placental Abnormalities and Imaging Features:

Morphological abnormalities:

1. Succenturiate placenta: Succenturiate placenta is a rare condition where there are one or more accessory lobes or smaller, separate placental masses connected to the main placenta by blood vessels. It's typically diagnosed through ultrasound imaging during pregnancy.[1],[2].

Imaging in ultrasound shows:

•  Identification of multiple placental lobes separated by a membrane.(figure 1)
• Visualization of blood vessels connecting the accessory lobes to the main placenta.
• Doppler ultrasound can be used to evaluate blood flow within the vessels.

It's important to note that while succenturiate placenta itself might not cause issues, it can be associated with complications such as placental insufficiency, vasa previa, and postpartum hemorrhage. Therefore, accurate imaging and diagnosis are crucial for appropriate management and monitoring during pregnancy.

2. Circumvallate placenta:

Circumvallate placenta is a condition where the placental edge folds back upon itself, creating a thickened ring or fold at the margin. This condition is usually diagnosed through ultrasound imaging.[3],[4].

On ultrasound, circumvallate placenta may appear as a thickened placental edge with a double-layered appearance due to the folded-over edge. This can sometimes resemble a "double ring" or "double fold" appearance on imaging. (Figure2)

Other findings may include decreased placental thickness or infarcts due to compromised blood flow at the site of the circumvallation. Doppler ultrasound may reveal alterations in blood flow patterns in the placenta, such as increased resistance or altered waveforms.

It's important to note that circumvallate placenta can increase the risk of complications during pregnancy, such as placental abruption or intrauterine growth restriction, so careful monitoring and management by healthcare providers are necessary.

3. Abnormalities of placental location:

Placenta Previa:

• Defined as the abnormal implantation when placental tissue either covers or is within 2 cm of the internal cervical os.[5]
• Ultrasound demonstrates placental tissue covering the cervical os, often associated with painless vaginal bleeding. (figure 3)
• MRI provides additional information on placental location, degree of coverage, and associated complications.

    4. Placentation abnormalities: Placenta Accreta, Increta, and PercretaPlacenta accreta refers to the extension of placental tissue to the myometrium without actual invasion. Placenta increta refers to the invasion of placental tissue into the myometrium without extension beyond the serosal surface. Placenta percreta refers to the invasion of placental tissue beyond the uterus.         A) Placenta Accreta:

• Ultrasound may show loss of the normal hypoechoic retroplacental zone and abnormal placental vascularity. (figure4)
• MRI is often used for further characterization and assessment of the degree of invasion into the uterine wall and adjacent structures.

                B) Placenta Increta and Percreta:

• Ultrasound may show loss of the retroplacental clear space and invasion of placental tissue into the myometrium (increta) or beyond (percreta).
• MRI can provide more detailed information about the extent of invasion and involvement of adjacent structures such as the bladder or bowel.

5. Placental Abruption:

• Characterized by premature separation of the placenta from the uterine wall before delivery.
• Ultrasound reveals retroplacental hemorrhage with disruption of the normal placental margins.(figure5)
• MRI aids in differentiating acute from chronic abruptions and assessing extent and severity of hemorrhage.

6. Placental Insufficiency:

• Results from impaired placental function leading to inadequate fetal nutrient and oxygen supply.
• Doppler ultrasound demonstrates altered uteroplacental and fetoplacental blood flow patterns, such as elevated PI and decreased umbilical artery diastolic flow.
• MRI may show features suggestive of chronic hypoxic insult, such as placental T2-weighted signal abnormalities and fetal growth restriction.

7. Placental Infarctions:

• Reflect areas of ischemic necrosis within the placental parenchyma.
• Ultrasound may depict hypoechoic or echogenic lesions within the placenta, often associated with decreased perfusion on Doppler imaging.(figure6)
• MRI can delineate infarcted areas with characteristic T1 and T2 signal changes, aiding in differentiation from other placental lesions.

8. Placental Tumors:

• Rare neoplastic lesions arising from placental tissue, including chorioangiomas and placental mesenchymal dysplasia.
• Ultrasound and MRI help in characterizing the size, location, vascularity, and tissue composition of placental tumors, guiding management decisions.

• Trophoblastic placental tumors, such as gestational trophoblastic disease (GTD), can manifest with various radiological findings depending on the specific subtype and stage of the disease.

Here are some common radiological imaging findings associated with trophoblastic placental tumors:

1. Ultrasound (US):

• Invasive mole: Irregular thickening of the placental bed with a heterogeneous echogenic pattern.
• Choriocarcinoma: Hypoechoic mass with areas of cystic degeneration and increased vascularity on color Doppler imaging.
• Hydatidiform mole: Grape-like vesicles with cystic spaces of varying sizes (figure7). Complete mole typically shows a "snowstorm" appearance with no fetal parts visible.[6].

2. Magnetic Resonance Imaging (MRI):

• Invasive mole: Placental bed infiltration with irregular margins and heterogeneous signal intensity on T2-weighted images. (figure8)
• Choriocarcinoma: Solid mass with areas of hemorrhage and necrosis, which appear hyperintense on T1-weighted images and hypointense on T2-weighted images.
• Hydatidiform mole: Enlarged uterus with a heterogeneous signal intensity on T2-weighted images. Complete mole may show diffuse and intense enhancement due to increased vascularity.

3. Computed Tomography (CT):

• Invasive mole: Diffuse thickening of the placental bed with heterogeneous enhancement.
• Choriocarcinoma: Soft tissue mass with areas of necrosis and hemorrhage showing heterogeneous enhancement post-contrast administration.
• Hydatidiform mole: Enlarged uterus with diffuse or focal areas of low attenuation representing cystic spaces, and enhancement of the molar tissue post-contrast administration.

These imaging modalities play a crucial role in the diagnosis, staging, and follow-up of trophoblastic placental tumors, aiding clinicians in treatment planning and monitoring response to therapy. It's essential to interpret these findings in conjunction with clinical history and other diagnostic tests for accurate diagnosis and management.

  Accurate diagnosis and characterization of placental abnormalities through radiology imaging are paramount for appropriate patient management and counseling. Timely identification of high-risk conditions allows for proactive obstetric management, including close fetal surveillance, antenatal monitoring, and timely delivery planning. Multidisciplinary collaboration between radiologists, obstetricians, and neonatologists is essential for optimizing maternal and fetal outcomes in cases of placental abnormalities.