Zur Systematik einer Pathologie der menschlichen Placenta

Association of Placental Jets and Mega-Jets With Reduced Villous Density

Spiral arteries (SAs) lie at the interface between the uterus and placenta, and supply nutrients to the placental surface. Maternal blood circulation is separated from the fetal circulation by structures called villous trees. SAs are transformed in early pregnancy from tightly coiled vessels to large high-capacity channels, which is believed to facilitate an increased maternal blood flow throughout pregnancy with minimal increase in velocity, preventing damage to delicate villous trees. Significant maternal blood flow velocities have been theorized in the space surrounding the villi (the intervillous space, IVS), particularly when SA conversion is inadequate, but have only recently been visualized reliably using pulsed wave Doppler ultrasonography. Here, we present a computational model of blood flow from SA openings, allowing prediction of IVS properties based on jet length. We show that jets of flow observed by ultrasound are likely correlated with increased IVS porosity near the SA mouth and propose that observed mega-jets (flow penetrating more than half the placental thickness) are only possible when SAs open to regions of the placenta with very sparse villous structures. We postulate that IVS tissue density must decrease at the SA mouth through gestation, supporting the hypothesis that blood flow from SAs influences villous tree development.

Karyotype and placental structure of first-trimester spontaneous abortions: a morphometrical study

Size of placental villi, thickness and condition of trophoblast, stromal density of villi as well as perivillous fibrinoid deposits were used as criteria for patho-morphological classification of karyotyped first-trimester spontaneous abortions. Significant differences in all the criteria were noted. Diagnostic values were verified using discriminant analysis. Using morphological values, 67% of the cases could be grouped correctly. Including further criteria (week of gestation, age of mother) it was possible to improve this to 72%. Normal karotype and trisomy could be accurately diagnosed using morphology; however, it is not suitable for finding monosomy X and tetraploidy.

Morphology of placental villi after premature delivery and its clinical relevance

Based on a new concept of maturation of the placental villous tree and its disorders (synchronous and asynchronous immaturity, asynchronous maturity, hypermaturity, and terminal villi deficiency) we studied the possible effect of the placental villous tree on the premature onset of labour. In mature normal neonates irregular and asynchronous villous patterns were found in 50% of cases. In prematurely delivered neonates, only 33% of the corresponding placentas show synchronous immature villous patterns. Uterine bleeding in the first trimester was associated with a 42% of incidence of premature maturation of the villous tree. These findings strengthen the idea that hormonal imbalance in early pregnancy influenced villous development. In "prematurity without recognizable cause" there was a higher percentage of villous maldevelopment (33%) than that previously described in the literature. In severe pre-eclampsia combined with premature onset of labour, 60% of our cases showed hypermaturity of the villous trees. Synchronous immaturity was reduced to 15%. We conclude, that even a rather rough definition of the histological features of placental villi is sufficient to produce numerous correlations between clinical events preceding premature delivery and placental structure. So the influence of placenta on the premature onset of labour needs more attention.

Amniotic epithelium in rhesus incompatibility: light and electron microscopic examination

Human amniotic epithelium from patients with normal pregnancy (normal amniotic epithelium) and from patients with materno-fetal rhesus incompatibility has been examined under the light and electron microscope. In comparison with normal amniotic epithelium, the epithelium in rhesus incompatibility displays the following morphological changes: 1. Unequal distribution and variable shape of the plump microvilli 2. Considerable narrowing of the intercellular spaces 3. Vacuolization of the cytoplasm 4. Absence of glycogen granules 5. Thickening of the basal membrane. There is a direct correlation between the morphological changes in the amniotic epithelium and the severity of the disease. Since rhesus factors are present only in erythrocytes, it is probably that these changes are not based on a direct immune conflict. On the contrary, they are more likely due to fetal hypoxia and to the cytotoxic effect of unbound, unconjugated bilirubin in the amniotic fluid.

[Problems of distinction of normal, arteficial and pathological structures in mature human placental villi. III. Morphometric studies in rhesus incompatibility (author's transl)]

Sections of human placental villi which were up to 80 micrometer in diameter were examined light microscopically and morphometrically. The villi were obtained by taking an aspiration biopsy of the attached placenta from 20 normal patients at term and from eight patients delivered at or before 37 weeks because of varying degrees of rhesus incompatibility. The distribution of three histological types of villi was determined. The intermediate villi from patients with erythroblastosis showed an increase in number and volume matching the severity of the disease. The intermediate villi also showed an increase in the amount of cytotrophoblasts, in the amount of materno-fetal diffusion surface area, in the thickness of syncytium, and in the number of Hofbauer cells. The terminal villi were not affected by erythroblastosis and the mature end villi showed a relative decrease in number. To obtain these results an optimal fixation technique was required.

Mathematical, clinical, and laboratory study of hemodynamic changes in the placental circulation

Various rheological properties of blood were investigated in pregnant and non-pregnant women of similar age. The results from 27 women with abnormal pregnancies were compared to those obtained from 17 non-pregnant women. In abnormal pregnancies we found a reduction of the erythrocyte filtration and a pathological use in red cell aggregation and in the shear resistance of the aggregates. Fractional light transmission (T7/T0) was higher than 1.0, suggesting that pressure gradients in the capillary circulation are not sufficient to disperse red cell aggregates. Thus, rheological factors may be partly responsible for the clinical consequences of pre-eclampsia. Pathological red blood cell aggregation and stagnation are consequences of the changed flow properties in the microcirculation. Even a small decrease of the local pressure gradients in the microcirculation of patients with pre-eclampsia would impair the dispersal of red blood cells and lead to their increased aggregation. Complete occlusion of the placental circulation by these aggregates would impair oxygen transfer at a speed that has been calculated from a diffusion equation based on the concept of the placenta as a hollow cylinder.

Massive subchorial thrombohaematoma (Breus' mole)

Ten placentae with massive subchorionic thrombohaematomas are reported. This lesion, which is composed of maternal clotted blood, separates the chorionic plate of the placenta from the villous chorion and is traversed by the main cotyledonary branches of the fetal circulation. In some instances it dissects into the layers of the chorionic plate. In anatomical terms it is identical to the lesion which has been described in early pregnancy under the title of Breus' mole. Previous reports suggested that the lesion was confined to early pregnancies and was a consequence of fetal death. In our series all ten placentae were from pregnancies of at least 25 weeks' maturity and six were more than 30 weeks. Seven infants were liveborn and three survived the neonatal period. Differential diagnosis is discussed along with aetiology, which is still obscure although earlier theories implicating fetal death may be discounted.