Measurement of human fetal growth

Perinatal mortality and morbidity are linked not only to gestational age but also to fetal growth. The antenatal recognition of intrauterine growth retardation (IUGR) is therefore one of the primary aims of obstetric care. However, for years clinicians have confused size with growth. Size is an endpoint, typically weight at birth, whereas growth is the process by which this endpoint is reached. Size is determined by a combination of local factors in tissues and organs, together with systemic nutritional and endocrine factors. Genetic influences, which are the primary determinant of fetal size, probably act primarily at the local level. Systemic factors are, in a sense, secondary, because although they might direct the growth process they do not determine size other than at pathological extremes (Chard, 1989).