Intrauterine growth retardation (IUGR) is associated with significant perinatal morbidity and mortality. This condition can be a sign of genetic disorders, fetal infection, uteroplacental insufficiency, or constitutionally small fetuses. Correct determination of gestational age is the first step in prenatal screening of growth-retarded fetuses. The discovery of a small-for-gestational age fetus necessitates fetal assessment for the evaluation of the etiology and prognosis, and for the determination of the optimal timing for delivery of these fetuses at risk of perinatal asphyxia. IUGR is more frequent in multiple-gestation pregnancies (23-34%) and will be discussed separately. There is no medical treatment for IUGR. Early aspirin treatment reduces the incidence of IUGR in a high-risk population but should not be used routinely in all pregnant women.