Fetal growth and development.

The foetal growth is, for the greater part, determined genetically. There are, however, favouring and inhibiting factors, which influence this growth. In such a matter, the mother, the placenta and the foetus play an important part. The mother shows as well metabolic as vascular adaptations. The placenta must let through nutrients and oxygen; the uteroplacental circulation is characterized by a high flow, together with a low vascular resistance. The foetus itself plays an important part owing to its own growth factors. The principal growth factors are insulin and the growth factors analogous to insulin. The slowing up of the intra-uterine growth is the consequence of genetic factors or of the decrease of the growth-potential. The real cause is, however, mostly a decrease of the vascular adaptation in the mother or a diminution of the uteroplacental circulation. The vascular causes usually induce an asymmetrical delay in the growth; foetal causes induce a symmetrical retardation. An exaggerated growth of the foetus--or macrosomy--is mostly due to an excessive inflow of nutrients: this is the case when a pregnant woman is suffering from diabetes. During the former years, it has become evident that abnormalities of the foetal growth influence the later life of people.