Although intra-uterine growth can be monitored effectively and postnatal size can be accurately measured, it is still difficult to differentiate between undergrown and small normal infants. Biochemical measurements are of little help, but arm anthropometry looks promising. Infants who are undergrown have certain physiological handicaps in the neonatal period, such as impaired nutrient absorption and increased resting metabolism, which add to their nutritional difficulties. More studies on the physiological differences between undergrown and normal infants may help to improve the precision with which they may be distinguished.
