Tracking a preemie's growth and development

  • Your preemie has two different ages to consider: his corrected age and his chronological age.
  • Using a growth chart during your preemie’s development is important.

Preemies grow and develop at a different rate than babies born at full term (39 to 40 weeks after conception).

Growth and development can be a challenge for premature babies, especially those that were born very small. Since your preemie was born before his body had the chance to mature, it may take him longer to reach certain milestones than if he had been born at term. 

Remember that every baby develops at their own pace. After your baby goes home from the NICU, his pediatrician will monitor his growth and development closely.

Corrected age

Your preemie has two important ages that your baby’s doctor will use to talk with you about growth and development:

  • Chronological age: The number of weeks or months since your baby’s birth. This is your baby’s age based on his date of birth.
  • Corrected age: Your baby’s actual age in weeks (chronological age) minus the number of weeks your baby was born premature. This is your baby’s age based on your due date.


For example, if your baby is 10 weeks old, but he was born 6 weeks early, you subtract 6 from 10 to get a corrected age of 4 weeks. 

Corrected age (also called “adjusted age”) takes into account the fact that your baby did not have 40 weeks of growth and development in your womb. It gives you a more realistic idea where your baby may be in his development. 

Use your baby’s corrected age for tracking growth and development until he’s 2 to 3 years old.

Catch-up growth

Many preemies experience a growth spurt before they’re 2 to 3 years old. As these babies catch up, any difference in size between preemies and babies born at term is decreased. 

Some preemies don’t experience catch-up growth until they’re older, so their growth and development will be more gradual. Talk with your child’s doctor if you have any questions or concerns about how your child is growing and developing. 

Understanding growth charts

Growth charts are a very important tool to help track your baby’s growth. They track the rate of your baby’s growth and can help your baby’s doctor detect a nutrition or health problem early.

It’s important to remember that your baby’s corrected age should be used to track his growth on a growth chart. This takes into account the number of weeks he was born early, and provides a more realistic picture of how he is growing. 

Growth charts are very helpful for tracking growth to make sure he doesn’t grow too quickly or too slowly.

Your baby’s growth and development can be affected by many things, including how long he was in the hospital, how small he was at birth, and medical problems or surgeries. 

You know your baby best

If you feel he is falling behind or you have questions about his growth or development, then talk to his doctor or a member of his healthcare team for help.

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