Some aspects of placental function.

THE PERINATAL Mortality Survey has shown that deaths due to anoxia during and before labour account for 10.5 in every 1,000 deliveries (Butler and Bonham, 1963). It is believed that the majority of these intrauterine deaths are due to an abnormality of the placenta (Potter, 1961). Although in some such cases an anatomical lesion of the placenta may be found, as for example, in retroplacental haemorrhage, placental infarction and massive thrombosis of the placental blood vessels, in most cases there is no anatomical lesion in the face of obvious physiological failure. It is because of this that an important obstetrical research problem at the present time is the development of a placental function test (Corner, 1964). Such a study must be based on an understanding of the constitution of normal placental activity, and the following discusses some of the present-day knowledge of those aspects of the structure and function of the placenta which are related to transport of naturally occurring substances. Whilst many instructive data have resulted from observations made on humans, the possible risk to mother and foetus precludes the employment of a number of useful experimental techniques, and so much information has been gained from the use of other animals. From such studies it is possible to conclude that the foetus is a highly independent organism physiologically. This is probably mediated in the placenta whose cells are not passively equilibrating with those of the mother, but are metabolically very active. However, there still remains doubt as to the actual anatomical location of the placental barrier.