Adjusted age, often referred to as corrected age, is a measurement used to accurately track the growth and development of babies born prematurely. This concept acknowledges that infants born before the typical 40 weeks of gestation missed valuable time for development in the womb. It is primarily applied to babies born before 37 weeks, who are considered preterm. Using this adjusted timeline helps set realistic expectations for when a premature baby should achieve common developmental goals. Pediatricians use this tool to monitor progress and help parents understand their child’s unique timeline.
Calculating Adjusted Age
Calculating a premature baby’s adjusted age involves a straightforward subtraction from their current age, known as their chronological age. To find the adjusted age, one must first determine how many weeks the baby was born early by subtracting their gestational age at birth from 40 weeks. That period of prematurity is then subtracted from the current chronological age. For example, if a baby is currently six months (24 weeks) old but was born eight weeks early (at 32 weeks gestation), their adjusted age is 16 weeks, or four months. This calculation gives the age the baby would be if they had been born on their original due date.
Developmental Milestones and Adjusted Age
The primary reason for using adjusted age is that premature infants are less mature than a full-term baby of the same birth date. Their brains and neurological systems require time to catch up. Therefore, assessing developmental milestones based on their adjusted age provides a far more accurate picture of their progress.
For instance, a full-term baby is expected to be sitting up independently between four and seven months of age. If a baby was born two months early, they might not be expected to sit up until they are chronologically six to nine months old. Milestones such as social smiling, rolling over, grasping objects, and walking are all evaluated against this adjusted timeline. Using this corrected age prevents premature infants from being incorrectly labeled as having a developmental delay.
When Correction Is No Longer Needed
The practice of using adjusted age is discontinued once a child reaches a point where they have caught up developmentally to their peers. Most pediatricians recommend tracking milestones using the adjusted age until the child is about two years old chronologically. The American Academy of Pediatrics aligns with this recommendation, suggesting correction is unnecessary after 24 months of chronological age.
While two years is the common benchmark, some healthcare providers may continue the adjustment for developmental assessments up to age three, especially for children born very early. By this age, the differences in developmental timing have usually diminished significantly. Although developmental monitoring reverts to chronological age, physical growth, such as height and weight, may still be tracked using specialized preterm growth charts for a longer period.