Newborn screening programs can prevent some cases of mental retardation by identifying inherited conditions that may lead to retardation. All states in the United States require a blood test for congenital hypothyroidism and phenylketonuria (PKU). Infants with PKU cannot metabolize the amino acid phenylalanine, found in foods that contain protein. Once identified, these infants can be given a low-phenylalanine diet that prevents retardation. Some states require newborn screening for additional inherited diseases.
Adult screening tests can identify carriers of other conditions before couples conceive a child. Individuals and couples with a family history of mental retardation can seek genetic counseling to evaluate their own risks and need for screening. Specialized laboratory tests, including amniocentesis, can detect Down syndrome and other genetic disorders in the early stages of pregnancy.
Proper prenatal care, avoidance of alcohol and drugs during pregnancy, and routine immunization against measles and other childhood diseases can prevent some forms of retardation. With pregnant women at risk of bearing a baby with a very low birth weight, magnesium sulfate treatments can reduce the risk of mental retardation in the infant by 70 percent.
New ways of preventing mental retardation may emerge as the Human Genome Project identifies more disease-causing genes. This research may lead to new screening tests and gene therapies that can remove defective genes that cause mental retardation and replace them with normal genes.