A number of interventions are available to reduce morbidity and mortality in fetuses with intrauterine growth restriction (IUGR); but these can only be implemented appropriately with timely diagnosis and monitoring. Prenatal diagnosis of these conditions can aid in decision making concerning the timing and route of delivery, thereby reducing perinatal risk. Regulation of fetal growth is multifactorial and complex. Optimal fetal development depends on genetically predetermined growth potential, and is modulated by fetal, maternal, placental, and environmental factors. The role of Doppler ultrasonography is also discussed. Abnormally small fetuses as a group have a relatively poor prognosis because some of the causes of subnormal size, such as inadequate supply of oxygen and nutrients through the placenta, chromosomal anomalies, and infections, adversely affect fetal outcome. Disturbances of fetal growth — intrauterine growth restriction (IUGR) and macrosomia — are associated with increased risk of perinatal morbidity and mortality. Prenatal diagnosis of these conditions can aid in decision making concerning the timing and route of delivery, thereby reducing perinatal risk.