Placental Pathologic Features in Fetomaternal Hemorrhage Detected By Flow Cytometry

Abstract

Background Fetomaternal hemorrhage (FMH) is a poorly understood entity that can have significant clinical effects. Flow cytometry is a reliable and relatively new method for FMH diagnosis. The objective of this study was to correlate placental pathology with FMH detected by flow cytometry. Methods All patients with available placentas and FMH flow cytometric testing performed from 2009 to 2015 were retrospectively reviewed. Cases were defined as ≥0.10% fetal red blood cells (RBCs) in the maternal circulation while controls contained <0.10%. Placental findings associated with FMH were determined. Results In this study, 35 cases and 79 controls were identified. Villous dysmaturity/immaturity was significantly more prevalent among the cases compared to the controls. Placentas with villous edema and nucleated RBCs (nRBCs) in fetal vessels were associated with greater mean volumes of fetal blood in the maternal circulation. Fetal and maternal vascular pathology was more frequent in the controls. When the cases were stratified into mild (<30 mL), moderate (30 mL-100 mL), and severe (>100 mL) FMH, nRBCs, villous dysmaturity/immaturity, and villous edema were all positively correlated with increasing FMH severity. The cases were more likely than the controls to display ≥2 of these 3 features. Fetal nRBCs within fetal vessels were semi-quantified and moderate to severe numbers of nRBCs were associated with higher mean volumes of fetal blood in maternal circulation. Conclusions Villous dysmaturity/immaturity, villous edema, and nRBCs in fetal vessels, findings compatible with fetal anemia, in addition to relatively few chronic placental changes, are the most significant placental findings in FMH detected by flow cytometry.

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“…Placental studies from pregnancies with Rh-negative mothers and Rh-positive fetuses showed a correlation between fetal cells in maternal circulation and placental lesions such as intervillous thrombosis, Kline's hemorrhages, placental infarcts, and retroplacental hemorrhages. Placentas with villous edema and nucleated red blood cells in fetal vessels and villous dysmaturity or immaturity were associated with greater volumes of FMH and higher severity of clinical presentation [5,6].…”