Developmental Delay is usually a diagnosis made by a doctor based on strict guidelines. Usually, though, the parent is the first to notice that their child is not progressing at the same rate as other children the same age. If you think your child may be “slow,” or “seems behind,” talk with their doctor about it. In some cases, your general pediatrician might pick up a delay during a well child visit or other meetings. It will probably take several visits and possibly a referral to a developmental specialist to be sure that the delay is not just a temporary lag. Special testing can also help gauge your child's developmental level.

Developmental delay can have many different causes, such as genetic causes (like Down syndrome), or complications of pregnancy and birth (like prematurely or infections). Often, however, the specific cause is unknown. Some causes can be easily reversed if caught early enough, such as hearing loss from chronic ear infections, or lead poisoning.

If you think your child may be delayed, you should take them to their primary care provider, or to a developmental and behavioral pediatrician or pediatric neurologist. An alternative to seeing a specialist is to work through your local school system (see below). If your child seems to be losing ground—in other words, starts to not be able to do things they could do in the past—you should have them seen right away. If your child is developmentally delayed, the sooner you get a diagnosis, the sooner you can begin appropriate treatment and the better the progress your child can make.