Excerpt

The human placenta secretes large quantities of specific proteins, protein hormones and steroids (Chard & Grudzinskas 1992a). Yet most of these products have no obvious function, either in the mother or the child, and it has even been suggested that placental hormones are the waste products of some underlying but ill-understood phenomenon (Gordon & Chard, 1979). Here a new hypothesis is put forward which might provide a solution to this biological enigma. It is proposed that the function of many of the specific placental products is not, as in classical endocrinology, to act as messengers and exert their efforts at distant sites. Instead, they serve to provide the placental syncytiotrophoblast with information about the maternal environment. In turn, this enables the trophoblast to function as a single, coherent tissue, both for secretion of specific products and, of far greater importance, as an organ for exchange of nutrients and waste