The effects of cigarette smoking on the human placenta: a light and electron microscopic study.

A histological and electronoptical study of placentae from women who smoke cigarettes during pregnancy shows a tendency towards a paucity of vasculosyncytial membranes, villous cytotrophoblastic cell proliferation, focal syncytial necrosis, decreased syncytial pinocytotic and secretory activity, dilatation of syncytial rough endoplasmic reticulum, abnormalities of syncytial microvilli, focal infolding of the free plasma membrane of the syncytiotrophoblast, degeneration of isolated cytotrophoblastic cells, irregular thickening of the trophoblastic basement membrane and degeneration of villous capillary endothelial cells. It is thought that many of these changes are due to placental ischaemia consequent upon nicotine-induced constriction of the uterine vessels; some of the changes cannot be explained on this basis and it is suggested that these may possibly be due either to cadmium toxicity or to accumulation of polycyclic aromatic hydrocarbons. There is apparently some impairment of placental function in cigarette smokers but this is probably offset by the ability of the placenta to repair ischaemic damage and to undergo a compensatory hyperplasia.