Infants with Down syndrome will generally require more frequent medical checkups (e.g., well-child visits) to ensure and maintain good health. Some symptoms that commonly affect infants with Down syndrome must be identified shortly after birth and monitored. For example, babies with heart or gastrointestinal defects may require corrective surgery in infancy.

Infants with Down syndrome are usually born an average size but tend to grow more slowly than others. Because of this, throughout life, most people with Down syndrome will be smaller than their age peers.

Down syndrome infants frequently have poor muscle tone (hypotonia). This may lead to problems with sucking and feeding. These infants develop more slowly than other infants. They tend to sit up and reach other developmental milestones later than usual. Teething often occurs later and the teeth may erupt in an abnormal pattern. Digestive issues such as constipation are also common during infancy.

Early intervention services can be extremely helpful for Down syndrome patients. These are best started as early as possible. Regular physical therapy, for example, can help to build muscle tone and improve coordination so the infants can learn to sit up and crawl.