Developmental milestones are determined by the average age at which children attain each skill, therefore, statistically, about 3% of children will not meet them on time, but only about 15-20% of these children will actually have abnormal development. The rest will eventually develop normally over time, although a little later than expected.
A developmental delay occurs when your child has the delayed achievement of one or more of his milestones. This may affect your child's speech and language, his fine and gross motor skills, and/or his personal and social skills.