Placentas and foetal health

Summary The placenta provides many critical services to the developing foetus. Proper placental implantation, growth and function are necessary for normal foetal growth and development. Placental structure varies widely among species but all mammalian placentas have a convoluted materno‐foetal interface that may be quite simple or highly complex; the more complicated interdigitations tend to characterise smaller placentas that have limited areas of contact between the placenta and the endometrium. The intimacy of the contact between maternal and foetal tissue varies from apposition only, as in the equine placenta, to invasion of maternal vessels by foetal cells, as in man. Abnormalities identified in the human placenta provide insight into maternal and foetal diseases that affect pregnancy outcome.