The physiological determinants of fetal growth

Abstract

Placental and fetal growth depend upon a large number of factors. Accurate sequential measurement of fetal and placental growth in utero is difficult. There is no test of any single placental function. Multiple pregnancy is associated with a reduction in placental and fetal size. Endocrine and metabolic factors interact in a complex fashion which is not fully understood. In some instances there is clear evidence that fetal growth can be limited by umbilical or maternal placental blood flow. Chromosomal or antigenic dissimilarities seem to play a minor role. Intrauterine growth retardation continues to be important for the farmer and the obstetric physician and remains an intriguing intellectual problem. And we may well wonder whether there is a critical period of development when the size of an animal already attained determines its subsequent rate of growth, just as in some organ systems the chance to pass one critical phase of functional development may be lost for ever.