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 in the pathology lab. HEV
thrombi are characterized by a mix of thrombus (to include proliferating
endothelial cells) along with intact and fragmented RBCs.
Future Pregnancies (Obstetrical View):
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.
Sequelae in the Newborn (Pediatric View):
We have made this diagnosis in more than a few live-born cases.
In fact, I had thought that HEV was always found in stillbirths or almost-dead babies who died shortly after birth. My first instance of live-born HEV happened in the placenta of a baby whose parents have been close colleagues for decades. The baby had no adverse sequelae and grew up to be an excellent medical professional! This was an instance of a frightening placental diagnosis which turned out to be "false positive" for immediate or long-term adverse consequences (likely because the OB handled everything optimally during labor).
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.
- see the bibliography.
(file produced August 5, 1994;
posted August 2002; latest addition 31 July 2015)