Determining whether an 18-month-old baby is mentally retarded requires a multifaceted assessment based on the baby’s medical history, physical examination, diagnostic IQ test, adaptive skills test, and laboratory tests. If the diagnostic intelligence test result is significantly lower than the level of the same age group by more than two standard deviations, or if the IQ is <70, the baby can be diagnosed with mental retardation. In addition, if there are deficits in adaptive behaviors, for example, scores of ≤8 on the Social Life Abilities Scale, the diagnosis can also be made. Clinically, 18-month-old babies are often judged by the Infant-Junior High School Social Life Skills Scale and the Wechsler Intelligence Test. If your child's development lags significantly behind that of his or her peers, we recommend that he or she be seen by a child health care provider in a timely manner, and that he or she be treated according to the doctor's instructions.