A methodical gross examination should be undertaken in all births and the results incorporated in the patient’s record.

The Pathology of the Human Placenta

A methodical gross examination should be undertaken in all births and the results incorporated in the patient’s record

Calcium metabolism in pregnancy: A review

Most placentas are normal, as are most babies. Therefore, an examination of all placentas may not be warranted, although this has been advocated repeatedly. Practical guidelines, including indications for the examination, have been published by the College of American Pathologists (Langston et al. 1997). This reference describes in tabular form the major abnormalities and their association with clinical features. Booth et al. (1997) inquired what reasons constituted the submission of a placenta for examination and found, regrettably, that it was Cesarean section delivery. This is hardly a good reason, as will be seen. A large number of surgical deliveries are repeat sections and have little impact on perinatal problems for which placental examination might be useful. Altshuler and Hyde (1996), on the other hand, found that 92% of placentas for which an examination was requested by an obstetrician or neonatologist had relevant pathology. Salafia and Vintzileos (1990) made a strong plea for the study of all placentas by pathologists. We concur with this view, as the sporadic examination does not provide sufficient training for young pathologists and it does not allow the “routine” pathologist to obtain sufficient background knowledge as to what constitutes a truly normal placenta. Another reason for the examination of all placentas is today’s litigious climate; it makes study of placentas highly desirable (see Chap. 27). Furthermore, it has been shown repeatedly that a placental examination is needed to understand the causes of perinatal deaths. This was demonstrated, especially for stillbirths, by the study of Las Heras et al. (1994). The most important lesions were found in the umbilical cord (18%), with inflammatory lesions being second. Altshuler (1999) wrote a searching essay on the “placenta-related epidemiology” from his vast experience in these matters. Because placentas differ widely in shape, size, and in appearance, the novice must become familiar with this spectrum of placental shapes. To do so, a large number of placentas must be examined routinely. In hospitals with large numbers of deliveries, however, it may be prudent to select placentas for examination by the pathologist.

Examination of the Placenta

The subcellular localisation of acid and alkaline phosphatase has been studied in the trophoblast of placentae from both normal and complicated pregnancies. In placentae from uncomplicated pregnancies the number of trophoblastic acid-phosphatase-containing organelles decreases progressively as gestation proceeds whilst alkaline-phosphatase activity, although abundant at term, could not be demonstrated during the early stages of pregnancy. The acid-phosphatase-containing organelles are of two types; one is a small round body which is probably a lysosome whilst the other is a multivesicular body. The alkaline phosphatase is distributed mainly on the syncytial microvilli and plasma-membrane. It is suggested that the marked lysosomal activity during early pregnancy is related to the architectural refashioning of the placenta during this period and that there are two phosphatase-linked transfer systems in the trophoblast, one dependent upon acid-phosphatase-containing multivesicular bodies and being utilised during early pregnancy and the other reliant upon alkaline phosphatase and dominating during the second half of gestation. In placentae from prolonged pregnancies there is a further decrease in trophoblastic acid phosphatase and, usually, a continuing increase in alkaline-phosphatase activity. In placentae from babies of low birth weight this trend is sometimes reversed and alkaline-phosphatase activity either disappears or its reaction product diffuses throughout the syncytium; this is usually accompanied by a marked increase in the number of acid-phosphatase-containing multivesicular bodies. Placentae from women with pre-eclampsia show no loss of alkaline-phosphatase activity but are characterised by an increased number of lysosomal bodies.

J. A. Plester

Papers

Calcium content of the human placenta.

The activity of alkaline and acid phosphatase in the human placenta

Serum isocitric dehydrogenase activity during pregnancy