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.
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