The age of an infant is typically measured by the time passed since birth, known as chronological age. For babies born prematurely (defined as birth occurring before 37 weeks of gestation), this standard measure can be misleading when evaluating development because they missed weeks or months of development in the womb. To account for this difference, medical professionals use “adjusted age,” a calculation that serves as a more accurate benchmark for assessing growth and developmental progress. This corrected time frame allows parents and caregivers to set realistic expectations for the baby’s timeline.
What Adjusted Age Means
Adjusted age, sometimes referred to as corrected age, is the age a baby would be if they had been born on their original due date. It provides a clearer picture of the baby’s developmental stage by factoring in the time lost due to early birth. Chronological age is simply the actual time elapsed since the baby’s birth.
The concept of adjusted age recognizes that a premature infant’s brain and body systems have not developed to the same degree as those of a full-term infant. Pediatricians use this corrected age to ensure they are comparing the baby’s progress against appropriate developmental averages. Using the chronological age alone would inaccurately suggest a developmental delay, potentially leading to unnecessary concern.
How to Calculate Adjusted Age
The process for determining adjusted age involves a simple subtraction that accounts for the weeks of prematurity. The calculation starts with the baby’s current chronological age and subtracts the number of weeks the baby was born before the standard 40-week gestation. The calculation is most often done using weeks rather than months to ensure accuracy.
The formula is: Chronological Age (in weeks) minus the number of weeks born prematurely. For example, a baby born at 32 weeks gestation was eight weeks premature (40 weeks minus 32 weeks). If this baby is now 16 weeks old chronologically, subtracting the eight weeks of prematurity results in an adjusted age of eight weeks. This means they should be expected to exhibit the developmental skills of a two-month-old full-term infant.
Tracking Developmental Milestones
The practical application of adjusted age is directly related to tracking physical, cognitive, and social milestones. Developmental milestones, such as smiling, sitting up, or crawling, are based on averages for babies born at full term. Using the adjusted age allows parents and healthcare providers to set realistic expectations for when a premature infant should reach these common goals.
A premature baby who is six months old chronologically but has an adjusted age of four months is not expected to be sitting up independently. Instead, their progress is measured against the expectations for a four-month-old, such as responsive cooing and pushing up on their arms during tummy time. Comparing a premature child’s progress to their adjusted age helps parents celebrate on-schedule development and avoids the stress of comparing them to full-term peers.
Discontinuing the Use of Adjusted Age
Adjusted age is a temporary measurement tool used while a premature baby is working to catch up developmentally. Most medical professionals advise parents and caregivers to stop using the adjusted age when the child reaches a chronological age of two years. Some sources suggest continuing the adjustment up to three years of age, especially for babies who were born very early.
By the time a child reaches two to three years old, the developmental differences between premature and full-term infants are often negligible. The majority of premature babies have successfully “caught up” to their peers, making the correction unnecessary for general developmental assessment. The child’s actual chronological age then becomes the standard measure for evaluating their ongoing progress.