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Ages & Stages

Your Baby's Growth & Physical Development: 1 to 4 Months Old

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From ages 1 to 4 months, your baby will continue growing at about the same rate they set during their first few weeks. Here's what you can expect during these months.

Getting bigger

In general, babies gain between 1.5 and 2 pounds (0.7 to 0.9 kg) and grow 1 to 1.5 inches (2.5 to 4 cm) each month during this period. Their head size will increase in circumference by about a half inch (1.25 cm) each month.

These figures are only averages, however. You can keep track of your child's development as it compares to average growth charts.

Head size & soft spots

At 2 months old, the soft spots (fontanels) on your baby's head should still be open and flat. But by 3 months, the one at the back should be closed.

Also, their head is more likely to be proportionately larger as compared to their body because it grows faster. This is normal; their body will soon catch up.

Looking longer & leaner: losing their "baby fat"

At 2 months, your baby will look round and chubby. As they start using their arms and legs more actively, though, muscles will develop. Their bones also will grow rapidly.

As their arms and legs loosen up, their body and limbs will seem to stretch out, making them appear taller and leaner.

Remember

If you have any questions about your baby's growth and what they look like at this age, talk with their pediatrician.

More information

Last Updated
4/7/2026
Source
Adapted from Caring for Your Baby and Young Child: Birth to Age Five 8th edition (Copyright © 2024 American Academy of Pediatrics)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.