•  The large villus on the right is involved by villitis

•  The villus on the left is normal.

•  Note the inflamed villus has no identifiable circulation.

•  The inflammatory cels are lymphoctyes and macrophages.

• Approximately 5% associated with viral infections such as CMV or parvovirus B19, listeria or other organisms

• Vast majority are non-specific or of unknown etiology

• In cases caused by organisms the infection reaches the placenta via the maternal circulation

• The organisms breach the villi and involve the stroma with a fetal inflammatory response

• In non-specific villitis the cells first accumulate in the intervillous space ("intervillositis") and then cross into the villus stroma

• These cells are maternal CD3+ T cells.

• Other studies suggest that cells within the villus may be either fetal or maternal in origin.

• Between 5-10% of consecutive pregnancies

• Recurrent if not infectious

• Associated with intrauterine growth retardation and poor pregnancy outcome

• Recurrent (non-infectious variety)

• Associated with intrauterine growth retardation

• May also be associated with pregnancy induced hypertension

• May have pale granular appearance to villi

• Usually normal

• Mononuclear inflammation in the intervillus space

• Erosion of the trophoblast and trophoblast necrosis resulting in an irregular villus outline

• Agglutination of the villi

• Mononuclear inflammation within the villus stroma

• Plasma cells and lymphocytes as well as inclusions may be seen in viral infections

• Eventual destruction of the fetal circulation with hemosiderin deposition

• End result is avascular villus

• Benirschke K, Kaufmann P. Pathology of the human placenta, 3rd ed. New York: Springer-Verlag, 1995, pp. 596-601.

• Current literature from PubMed at National Library of Medicine