This rare disorder falls under a larger general heading of "thrombotic vasculopathy of placental fetal vessels", thromboses tending to be induced by endothelial injury, most often hypoxic. This broad category includes "vascular intimal cushions" (possibly reflective of an acute hypoxic episode⁵), chorionic plate "fetal artery thrombosis" (with or without associated villous infarction) (possibly reflective of an inherited thrombotic tendency⁷), hemorrhagic endovasculitis (HEV), and possibly other entities. For all practical purposes HEV cannot be diagnosed except by post-partum histologic examination of the placenta. HEV thrombi are characterized by a mix of thrombus (to include proliferating endothelial cells) along with intact and fragmented RBCs.

From 1980 through 1990, there was considered to be a significant risk of HEV recurrence in subsequent pregnancies⁸. Recurrence risk rate is presently uncertain. But, since the disorder is more likely in female infants and in cases of PIH, especially if there are prenatal indications of IUGR, recurrence of  HEV can be given prenatal consideration in such circumstances¹⁰. With HEV having a high association with stillbirth, management of a presumptive prenatal diagnostic consideration tends to be rapid and with a view toward avoiding stillbirth.

We have made this diagnosis in more than a few live-born cases. Neurological sequelae, from minor milestone delays to cerebral palsy, would appear to be related to (not acute) subacute and/or chronic fetal vascular insufficiency². Such subacute or chronic fetal hypoperfusion situations might be implied in HEV live-born cases associated with SGA/IUGR and/or a distinctly elevated fetal:placental weight ratio (no other competing basis having been identified), especially if the newborn has a distinctly elevated peripheral blood RBC count with definite erythroblastosis in the absence of HDN or a positive DAT. An impressive degree of chronic villitis (VUE) and/or villous ischemic lesions is said to also be a clue to possible increased risk of injury⁵. If the newborn appears to have neurological injury, then management is by standard methods. If there is no apparent abnormality, then care should be taken that the baby is seen at typical and standard times throughout childhood development in order to detect any milestone delays (in the same manner that one would calmly follow childhood development in order to detect any other type of problem) in order to allow early corrective intervention should delays be encountered⁶, any delays usually being so subtle as to not be encountered until after the age of one⁶ year old if at all. It is too premature in our understanding of possible sequelae to actually routinely discuss such risks with parents.

References:

1. see the bibliography.

(file produced August 5, 1994; posted August 2002; latest addition 27 July 2005)