Haemorrhagic endovasculitis of the placenta: a review with clinical correlation.

Haemorrhagic endovasculitis (HEV) is a recently described vasodestructive process within the placenta. Similarities to several forms of thrombotic microangiopathy are evident. Clinical studies have shown strong associations between HEV, still birth and intrauterine growth retardation (IUGR). Liveborn infants, with affected placentae, evaluated at the age of five, exhibit a high incidence of neurological abnormalities. HEV has been recurrent in successive pregnancies in some patients. Clinicopathological processes, which appear to be associated with HEV, include the presence of chronic villitis (VUA) and maternal hypertension. Viral- and/or Mycoplasma-type particles have been identified in a number of affected placentae examined by electron microscopy. Associated pathological events suggest an infectious aetiology possibly acting in concert with an environmental toxin. Biochemical factors and alterations of immune response within the maternal-placental-fetal unit may be involved.