Physical Development, Ages 1 to 12 Months

Overview

Babies grow quickly during the first year of life. Weight, length, and head circumference measurements are plotted on growth charts to monitor your baby's growth over time. Most babies:

• Grow about 3 in. (7.5 cm) to 4 in. (11 cm) in length by 4 months of age. Growth may slow slightly between 4 and 7 months of age. But by 12 months of age most babies have grown a total of about 10 in. (25 cm) in length since birth and are about 28 in. (71 cm) to 32 in. (81 cm) long.
• Gain an average of about 4 lb (2 kg) to 6 lb (2.7 kg) by 4 months of age. Birth weight usually doubles by 6 months of age. It triples sometime between 9 and 12 months of age.

The soft spots, or fontanelles, on top of a baby's skull start to close at 6 months.

When your baby is about 6 months old, teething may start. Teeth may not yet break through the gums at this age. But your baby may drool, chew on objects or hands, and act fussy from the pressure of new teeth coming in.

Keep in mind that each baby is different. Growth patterns can change between routine well-child checkups. If you have concerns, talk to your doctor about the many things that can affect your baby's growth.