Physical Development, Ages 1 to 12 Months

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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. Your baby grows at his or her own pace, and healthy growth is different for every baby. Your baby's natural growth rate may be slower or faster than the examples below. Most babies:

  • Grow about 7.5 cm (3 in.) to 10 cm (4 in.) 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 25 cm (10 in.) in length since birth and are about 70 cm (28 in.) to 80 cm (32 in.) long.
  • Gain an average of about 2 kg (4.5 lb) to 2.75 kg (6 lb) by 4 months of age. Birth weight usually doubles by 6 months of age and triples sometime between 9 and 12 months of age.
  • Have an increase in head circumference of about 0.5 cm (0.2 in.) to 1 cm (0.5 in.) 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.

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 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.


ByHealthwise Staff
Primary Medical ReviewerJohn Pope, MD - Pediatrics
Thomas M. Bailey, MD - Family Medicine
Specialist Medical ReviewerLouis Pellegrino, MD - Developmental Pediatrics

Current as ofSeptember 9, 2014