The age of a child from their date of birth is known as their chronological age. A baby born before 37 weeks of gestation is considered premature, meaning they missed several weeks of development inside the womb. Because of this lack of in-utero time, their body and brain have not reached the same biological maturity as a full-term infant of the same chronological age. Adjusted age is necessary to accurately evaluate a premature infant’s development and growth. Medical professionals use this measurement to provide a more realistic baseline for developmental expectations.
How Adjusted Age is Calculated
Adjusted age, sometimes referred to as corrected age, represents the age a premature infant would be if they had been born on their original due date. A typical, full-term pregnancy lasts 40 weeks.
The first step in calculation is determining the number of weeks the infant was born prematurely by subtracting their gestational age at birth from 40 weeks. The second step involves subtracting those weeks of prematurity from the child’s current chronological age. This adjustment provides the age that reflects the child’s true level of physical and neurological maturity. For example, a baby who is currently six months old chronologically but was born two months (eight weeks) early would have an adjusted age of four months. Using the adjusted age allows healthcare providers to compare the premature infant’s development to that of a child who is developmentally the same age.
Applying Adjusted Age to Developmental Milestones
Medical professionals use the adjusted age to set realistic expectations and assess a premature infant’s progress across all developmental domains. This practice is employed by pediatricians, physical therapists, and other specialists during routine check-ups. Using the chronological age alone would unfairly suggest a developmental delay when the infant is simply still maturing.
Motor skills are one of the most visible areas where adjusted age is applied. An infant born three months early, who is now chronologically six months old, would be assessed for skills expected of a three-month-old, such as developing better head control or starting to push up on their forearms. Milestones like sitting independently, crawling, and walking are all evaluated based on this corrected timeline.
The concept also applies to cognitive development, which includes skills like problem-solving and object permanence. Pediatricians will look for signs of cognitive readiness, such as tracking objects or reaching for a toy, at the age-appropriate time defined by the adjusted age. Similarly, language development, encompassing skills from cooing and babbling to speaking a first word, is benchmarked against the adjusted age. This assessment ensures that interventions, if needed, are provided at the correct time, accurately identifying a true developmental concern rather than mistaking a lack of maturity for a delay.
When Adjusted Age is No Longer Used
The practice of using adjusted age is not indefinite and typically ceases once the child reaches a certain chronological age. For most premature infants, the difference between their chronological and adjusted age becomes negligible between 24 and 36 months of age. By this time, the majority of premature children have neurologically and developmentally caught up to their peers who were born full-term. The nervous system and physical body mature significantly during the first few years of life, allowing the infant to close the developmental gap. After the 36-month mark, medical professionals generally use the child’s chronological age for all growth and developmental monitoring.