Knowing the difference between milestones and averages is super important when tracking a child’s development. If we think that milestones are the same thing as averages, children who are at risk of delays will get missed. For example, if a 3-year old has about 200 spoken words (instead of the “milestone” of 250 words), we might think “It’s OK, he/she is not that far behind”. But actually, it means that the child is not achieving the minimum for his/her age. (Remember, the average 3-year old has about 1000 words.) If we don’t understand this and don’t take action, then over time, the initial “mild” lag in development will result in widening gaps that will be harder to close the older the child gets.
Having said that, if your child is not meeting one milestone in an age range, it doesn’t necessarily mean something is not right. However, if your child is behind on multiple milestones, is not picking up new skills, or is losing skills that they once had, it may be a good idea to seek professional opinions.