Corrected and chronological age

When a baby is born before their due date, they will have two ages: their corrected age and their chronological age. Your baby also had a gestational age, which was the age of your baby from conception to birth, calculated in weeks.

When following your baby’s growth and development, it can be helpful to know the difference between the ages:

Corrected age: The age your baby would be if they had been born on their due date. For example, a baby who was born three months early (who now has a chronological age of seven months) has a corrected age of four months. Corrected age is useful while following your baby’s growth and development.

Chronological age: The age of your baby since birth. Your child's birthdays are celebrations of his or her chronological age.
To calculate your baby’s corrected age, start with your baby’s age in weeks (the number of weeks since birth) and subtract the number of weeks your baby was premature.

For example, Eli was born at 25 weeks gestation (15 weeks early) and 27 weeks have passed since his birth. His corrected age is 27 weeks – 15 weeks = 12 weeks or three months corrected.

For most pre-term babies, you will only need to correct their age until they are two or three years, as by this time most children have caught up developmentally to their peers.

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