Placenta Percreta

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PLACENTA PERCRETA is a rare but catastrophic obstetric complication. Reports of only 10 authenticated cases1–10 have been found in the English literature; we are presenting two additional cases.

To facilitate understanding of this clinicopathologic entity, we first shall describe pertinent features of normal placentation.

Aspects of Normal Placentation

The decidua basalis is that portion of the decidua underlying the placenta, and throughout its circumference is continuous with the decidua vera; it is composed of the compact, spongy, and basal layers. The surface of the compact layer is partially replaced by a fibrinous zone that is referred to as Nitabuch’s stria and which forms the boundary between fetal and maternal structures of pregnancy (Fig. la). Our observations, which indicate that separation of the placenta occurs beneath this plane, are confirmed by the presence of a thin layer of compact decidual tissue on the surfaces of separated placentas (Fig. 1 b). The spongy layer contains dilated maternal blood vessels in its stroma as well as occasional isolated trophoblastic cells that represent unorganized penetration through the compact layer. The basal layer is composed of a single zone of proliferating cells in juxtaposition to the myometrium.

The differentiation of Rohr’s stria and Nitabuch’s stria is not always clear-cut because they are similar histologically although they have different origins. Rohr’s stria, of fetal origin, is a fibrinous layer that lines the intervillous spaces; in the separated placenta this fibrinous layer is covered by syntrophoblast. Nitabuch’s stria is of maternal origin and is part of decidua basalis;. . .



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