The term "developmental delay" refers to a delay in attaining linguistic, cognitive, and motor ability milestones. Developmental delays can be caused by a number of reasons, including inheritance, prenatal complications, and preterm birth. The root cause isn't always clear. When there is no apparent cause for developmental delay, it's called idiopathic development delay. Language and motor skills are the first abilities to develop in infants and toddlers. A baby's brain is growing at many different times during these first years of life. If a problem arises when the brain is developing, it may cause problems with language and motor skills. For example, if a child receives an injury to the brain before developing full control of his or her limbs, he or she might experience language and motor skills delays as well. There are several types of developmental delays: mild, moderate, severe, and profound. Mild delays affect someone who takes longer than expected to learn new skills but eventually catches up. Moderate delays mean someone does not reach age-appropriate levels of performance on tests that measure specific skills. Severe delays indicate that someone reaches age-appropriate levels of performance but cannot perform routine tasks independently. Profound delays mean that someone cannot do anything beyond basic self-care. Developmental delays can be caused by genetic factors, such as disorders that affect the amount of neurotransmitters in the brain.