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The authors present a case of stillbirth in which histologic examination of the placenta provides the opportunity to make a definitive diagnosis of a death due to fetal thrombotic vasculopathy (FTV). Establishing the etiology in cases of stillbirth may avoid medical malpractice litigation. The better knowledge of the cause of stillbirths also helped obstetricians to recognize factors that could have prejudiced future pregnancies.

In Part IV of this review of placental pathology, reference is made to impaired maturation of the placenta under special clinical conditions. Foetal erythroblastosis is only of minor importance, in that context, today, while similar placental alterations may result from foetal hydrops of different genesis, including immunological causes. A detailed account is given of diabetic impairment of maturation together with possible placental diagnosis of diabetes. Cases of diabetes mellitus with concomitant EPH gestosis were found to be more strongly determined for placental differentiation by EPH gestosis. Reference, finally, is made to disturbed placental differentiation under conditions of EPH gestosis with or without concomitant impairment of intervillous circulation.

Placental pathology is rarely a part of the training for either obstetrician or pathologist. As a result there has been confusion regarding the potential benefits of routine placental examination. These benefits include clarification of the causes of many adverse pregnancy outcomes, improvement of the risk assessment for future pregnancies, and ascertainment of newborn risk for long-term neurodevelopment sequelae. Information on placental abnormalities may reveal the presence of chronic fetal insults and allow their differentiation from acute (peripartum) stresses. Current methods of risk assessment fail to identify the majority of pregnancies that end in prematurity, stillbirth, growth retardation, or fetal distress. We suggest that placental pathology should be a routine component of obstetric-neonatal care.

In this chapter, placental development, morphology, and indications for its examination have been reviewed. Techniques for placental examination with practical suggestions applicable to the surgical pathology laboratory have been pointed out. Several specific examples of clinical conditions in which morphologic alterations within the placenta assist with or establish a diagnosis have been presented. It is hoped that this information will encourage pathologists to use this important organ more fully as a resource in diagnoses and patient care.

In Rh-incompatibility the human placenta shows a prominent retardation of maturation. The placental insufficiency caused by these changes, combined with the existing hemolysis, represents an additional danger to the fetus. In a patient with severe Rh-incompatibility several Rh-negative blood transfusions were performed between the 26th and 30th weeks of gestation via sonographically guided puncture of the umbilical vein. Morphometric studies of the placenta were performed and the results compared with data already obtained from normal mature placentas and placentas from pregnancies complicated by Rh-incompatibility. Small terminal villi with a surface area identical to normal mature placentas were found. There was no improvement in vascularization when compared with other placentas from Rh-incompatible pregnancies. Nevertheless, isolated rebuilding of epithelial plates was found. The authors interpret these morphological phenomena as a "partial postmaturation" of the placenta as regards the development of the terminal villi. The absence of reproliferation of the villous vessels as well as the lack of any extensive regeneration of the epithelial plates could be due to the short time which elapsed between transfusion therapy and the inevitable indication for caesarean section. Intensive intrauterine therapy reduces the risk to the fetus due to immunologic complications, as well that due to placental insufficiency, as evidenced by the additional differentiation of villi.

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.

The latex injection-corrosion cast technique coupled with scanning electron microscopy was applied to the study of severe Rh sensitization of the placenta. The main observed ultrastructural changes in fetal vasculature in this type of placenta were very similar to those of the small for gestational age placenta; large-sized vessels exhibited less branching than those of the normal placenta, and the capillary network showed numerous vascular buds and "H"-shaped anastomoses. In addition, in Rh-sensitized placentas, the capillary network was remarkably sparse, and the cast also revealed smooth-surfaced veins with distinct U shapes undulating through the placental stroma. These U-shaped veins may be the result of umbilical flow impedance with subsequent umbilical venous hypertension, which stretches the veins into undulating form.

Principle possibilities of the complex evaluation of the mother-fetus exchange were studied by means of morphological investigations of the human placenta in normality, in vesicular mole, late toxicoses, hemolytic disease of newborns and malformations of the fetus. The investigation of the ratio of the villi of different size, deposition of fibrinoid on their surface, the change of the amount of cytotrophoblastic elements, cells of Kaschenko-Hofbauer and the polymerity of the basic substance are of diagnostic value. The authors propose the basal lamina of the placenta to be included into the scheme of the examination of placenta.