Blood can be tested when a baby is born to determine if they have Down syndrome. Also the distinct facial features can help diagnose it.

Low muscle tone and late development are very common for people with Down Syndrome.

Children with this condition should not be compared in development with other children. They are hard to compare considering the milestones are different.

The tendencies to learn and grow slower are some effects of this condition. Also the judgement and reasoning tends to be delayed and isn't as accurate as a normal child's skills would be.