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Placenta

Anomalies

Name:

Perivillous fibrin deposition

Description:

Perivillous fibrin is derived from the maternal blood in the intervillous space. The turbulence of blood within the intervillous space results in maternal platelet adherence to the villous syncytiotrophoblast with subsequent thrombosis. The areas of syncytiotrophoblast that become engulfed in fibrin are cut-off from their oxygen supply from the maternal blood and undergo ischemic necrosis. Perivillous fibrin deposition is present in approximately 20% of term placentae. It occurs less frequently in placentas after premature delivery (6%) and in the placentas of diabetic (6%) and pre-eclamptic (12%) women. It has been hypothesized that lower intervillous flow rates in insulin dependent diabetes mellitus and in pre-eclampsia, reduce the turbulence that is the precipitating factor in perivillous fibrin formation. Massive perivillous fibrin deposition refers to macroscopically visible plaque-like placental lesions. It is seen most frequently around the periphery of the placenta. The reported incidence of this more extensive lesion is 0.4%.

Diagnosis:

Perivillous fibrin deposits are indistinguishable from intervillous thrombus. In the majority of cases perivillous fibrin deposition is not clinically significant. Since the placenta has a significant reserve capacity, loss of up to 30% of placental function does not affect fetal oxygenation and nutrition. When over 50% of the placental villi are enveloped in perivillous fibrin, intrauterine growth restriction and intrauterine fetal demise have been reported.

Differential Diagnosis:

Placental hypoechoic lesions are quite common. Septal cysts, perivillous fibrin deposition and intervillous thrombosis are sonographically indistinguishable.

Sonographic Features:

Perivillous fibrin deposits appears sonographically as intraplacental hypoechoic or anechoic lesions.

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References


Clinical significance and treatment of massive intervillous fibrin deposition associated with recurrent fetal growth retardation.
Fuke Y, Aono T, Imai S, Suehara N, Fujita T, Nakayama M.
Gynecol Obstet Invest;38:5-9.

Macroscopic abnormalities of the placenta.
Fox H.
Chapter 5. In: Fox H. Pathology of the Placenta. 2nd edition. WB Saunders Company Limited.

Vascular anatomy of the human placenta and its significance for placental pathology.
Wiggleworth JS
J Obstet Gynaec Brit CommonW;70:579-89.