Definition: Developmental regression refers to a condition in which children reach their developmental milestones at the expected times but at some point they start to lose the skills they developed and the developmental milestones they have met. It may also be used to refer cases in which the child was developing at a normal pace but then his or her development seems to have stopped.

Developmental regression should not be confused with developmental delay, which refers to a condition in which the child does not reach the developmental milestones at the expected time.