Fibrin Deposition
Localized areas of perivillous fibrin deposition are seen in virtually all
mature placentas and show an irregular lacelike pattern (Figure 5.28,
Figure 5.29). Although the entrapped villi eventually die, small amounts
of fibrin deposition are not generally thought to be related to fetal or
maternal disease, apparently originating from turbulence in the mater-
nal circulation.
Occasionally fibrin deposition is excessive, diffusely involving half or
more of the villous tissue (Figure 5.30, Figure 5.31). This degree is abnor-
mal, and associated with preterm delivery, growth retardation, and death.
Fibrin Deposition 83
Figure 5.28. This
cross section shows a
thrombotic lesion (left)
and perivillous fibrin
deposition (right). The
shiny old thrombus is
actually an extension
of a small, old,
subchorionic
hemorrhage and not a
true intervillous
thrombus. Note the
irregular outlines of
the fibrin deposition
and its admixture with
normal villous tissue.
There is substantial
calcification in this
area.
Figure 5.29. The white material deposited in this term placenta is fibrin. Such
localized fibrin is common in later gestations. It is deposited in the intervillous
space around villi in a lacelike fashion, and usually is quite hard and shiny.
Although the entrapped villi eventually die, such fibrin deposition is not usually
associated with fetal or maternal disease. At times, relatively large regions are
involved, as shown here. The process, however, is still localized and not of
concern.