Purpose or Case Report: Placenta, one of the least understood human organs, is external to fetal body with genetic characteristics identical to the fetus. Placenta is made up of its parenchyma, membranes, and umbilical cord (UC). It involved in the transfer blood gases and nutrients, act as immune barrier, secrete hormones and other substances. Ultrasound, Doppler, and MRI are used to evaluate placental configuration and predict adverse outcomes. MR adds value to fetal and placental sonographic evaluation thanks to its wide field of view and high tissue contrast. Single shot fast spin echo (SSFSE), balanced steady state and T1-W, occasionally DWI, are the most used sequences. We present the spectrum of morphologies and pathologies of the placenta and UC on ultrasound and MRI.
Placental location and shape: Placental location is based on its relationship with the uterus and cervix. The placenta tends to migrate toward the fundus throughout pregnancy. Placental thickness ranges from 2-4 cm. It can be a single structure, bilobed or have an accessory lobe. Variations include circumvallate and placenta membranacea.
Placental signal: Normal parenchyma is intermediate to hyperintense on fluid sensitive images, more homogenous in the second trimester and progressively becoming lobulated and septated. Increased number and size of cotyledons make the placenta more heterogenous.
Placental hemorrhage: Blood pooling and hemorrhage are another cause of placental heterogeneity.
Placental-myometrial Interface: Best seen on steady state, displaying a trilaminar appearance.
Chorionicity: Chorionicity and amnionicity are determined on the first trimester ultrasound. MRI offers a larger field of view for evaluation of the membranes’ attachment and UC in the second and third trimesters.
UC insertion: UC inserted to the center of the placenta. Eccentric insertions, and velamentous insertions can be identified on MRI.
UC structure: The UC contains two umbilical arteries, a single umbilical vein, allantois duct and Wharton's jelly and is enclosed within the outer layer of amnion.
UC varix: This refers to the dilation of the fetal umbilical veins as it runs through the fetal abdomen.
UC cysts: Uncommon, differential diagnosis includes pseudocysts, omphalomesenteric duct cysts, vascular disorders, abdominal wall defects, bladder exstrophy and urachal anomalies.
Placental Tumors. Placental tumors are categorized in trophoblastic and non-trophoblastic. The latter include chorioangiomas, teratomas, and hemangiomas.
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