Impairment of either fetal growth potential or placental growth support may cause fetal growth retardation. Impaired growth potential is associated with a number of congenital abnormalities. Awareness of the increased possibility of fetal anomaly comes from the obstetric patient's reproductive history or family history more than from anything else. In general, if the likelihood of fetal anomaly seems increased, investigation in the form of amniocentesis, ultrasonic monitoring of fetal growth, radiologic study, or all three may be required. More common than poor growth potential is poor placental growth support. Here, historical evidence of maternal hypertension or toxemic disorders, among other abnormal clinical findings, is an indication for fetal monitoring.