Between 80 and 100 spiral arteries of the endometrium spill their contents into the intervillous spaces
and bathe the villi.
The epithelium covering the villi and the intervillous spaces
was pseudostratified columnar in type (Fig.
 Typical placental findings are retroplacental haemorrhages and (laminated) intervillous thrombi with NRBCs in fetal organs and intervillous spaces
.  Laminated intervillous thrombi (linear streaks of fibrin with degenerating red and white blood cells in between) are thought to be caused by leakage of fetal blood into the intervillous spaces
via defects in the trophoblast, usually occurring at varying times and leading to clotting of mixed fetal-maternal blood as a mechanism to limit fetal blood loss and fetomaternal bleeding.
Accumulation of infected erythrocytes in placental intervillous spaces
characterizes malaria during pregnancy (3).
The major functioning unit of the placental circulation is the chorionic villi, which is located in the intervillous spaces
. Maternal blood enters the intervillous spaces
through the spiral arterioles and bathes the chorionic villi.
The pathogenesis of PE, although poorly understood, has been associated with apoptotic change of the villous trophoblasts (11), possibly secondary to inadequate oxygenation of blood within the intervillous spaces
Within the intervillous spaces
, many of the maternal red blood cells were sickle shaped (Figures 1 and 2).
The intervillous spaces
were varying in width, but mostly small in size.
The absence of 2 stage of spiral arterial invasion causes dysfunctional perfusion of intervillous spaces
with oxidative and hemodynamic stress.
We recently reported that fetal DNA in maternal plasma is derived primarily from villous trophoblasts bordering the intervillous spaces
, which are filled with maternal blood (13).
Hyperplasia in the syncytiotrophoblasts, especially the syncytial layer develops sprouts protruding into the intervillous spaces
. Also in the field intervillos fibrinoid deposition, syncytial nodes and an increase was observed in the fetal capillaries Chorionic villous maturation, vascular dilatation and progression of villous congestion were also increased in the connective tissue