Fetal-Placental Interactions in the Control of Prenatal Growth

Abstract

During the course of prenatal development there is usually a very close relationship between the growth of the placenta and that of the fetus (1–4). This relationship does not necessarily persist throughout the whole of gestation and may not be particularly apparent early in fetal life. However as the fetus enlarges the relationship appears and dominates prenatal growth (3). Hence if placental size is restricted the growth of the fetus suffers in an almost proportionate fashion (2–4). The close relationship between the growth of these two structures is also reflected in a clear correlation between the extent of the perfusion of the maternal placenta and fetal growth (1,2,4,5). Such observations imply that one of the determining mechanisms underlying prenatal growth rate may be the substrate supply across the placenta. Although there is some evidence in favor of this mechanism it does not adequately explain control of prenatal growth and particularly maturation (6–9). In addition to its transport functions the placenta has a wide range of endocrine roles, one of which could be the control of prenatal growth (6). Although there are few clear indications of the mechanisms that could integrate substrate supply across the placenta with its endocrine functions there are indications that this is an important pathway regulating prenatal development (6–9). Some of the pertinants observations will be reviewed here.