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Physical Development, Ages 1 to 12 Months

Topic Overview

Babies grow rapidly 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. (7.6 cm) to 4.5 in. (11.4 cm) in length by 4 months of age. Although growth may slow slightly between 4 and 7 months of age, by 12 months of age most babies have grown a total of about 10 in. (25.4 cm) in length since birth and are about 28 in. (71 cm) to 32 in. (81 cm) long.
  • Gain an average of about 4.5 lb (2 kg) to 6 lb (2.7 kg) by 4 months of age. Birth weight usually doubles by 6 months of age and triples sometime between 9 and 12 months of age. This is an average gain of 0.5 oz (14 g) to 1 oz (28 g) a day for the first 6 months.
  • Head circumference grows about 0.25 in. (0.6 cm) to 0.5 in. (1.3 cm) a month.

The soft spots, or fontanelles, on top of a baby's skull begin to close at 6 months but won't completely grow together until sometime between the 9th and 18th month. See a picture of the soft spots.

When your baby is about 6 months old, teething may begin. 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.

It is important to keep in mind that each baby is different, and 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. Physical growth requires adequate nutrients and a nurturing environment.

Credits

By Healthwise Staff
Primary Medical Reviewer Susan C. Kim, MD - Pediatrics
Specialist Medical Reviewer Louis Pellegrino, MD - Developmental Pediatrics
Last Revised October 7, 2011

Last Revised: October 7, 2011

Author: Healthwise Staff

Medical Review: Susan C. Kim, MD - Pediatrics & Louis Pellegrino, MD - Developmental Pediatrics

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