What is corrected age?

Corrected age, also called adjusted age, is the age a premature baby would be if born on the due date. It is the chronological age minus the number of weeks the baby was born early, and it gives a fairer baseline for judging development and growth.

How is it calculated?

First find how premature the baby was by subtracting the gestational age at birth from 40 weeks. Then subtract that many weeks from the chronological age. For a baby born at 30 weeks, eight weeks early, a four-month-old has a corrected age of about two months.

Until what age should I correct?

Correction is conventionally applied until about 24 months. By two years the gap between premature and term infants has usually narrowed enough that chronological age can be used. Some teams continue correcting for very preterm infants slightly longer.

Why does it matter for milestones?

Judging a premature baby's development against its chronological age unfairly labels normal progress as delayed. Using corrected age means milestones such as smiling, sitting, and walking are compared against the time since the due date, which is when those abilities are expected to emerge.

Does a term baby need correction?

No. A baby born at 40 weeks has zero weeks of prematurity, so the corrected age equals the chronological age. Only infants born before term carry a correction, and the earlier the birth the larger the adjustment.

Corrected Gestational Age for Premature Infants

Premature babies should not be measured against the calendar alone. A baby born two months early has had two fewer months to develop in the womb, so comparing its skills against a baby of the same chronological age understates its progress. Corrected age fixes this by counting from the original due date.

How it works

The calculation has two simple steps. First, work out how early the baby arrived, then subtract that from the time since birth:

weeks premature = 40 - gestational age at birth (weeks)
corrected age   = chronological age - weeks premature

The tool computes the chronological age from the birth and assessment dates, converts the gestational age into a precise number of weeks premature including extra days, and reports the corrected age in months, weeks, and days.

Notes and example

A baby born at 30 weeks is ten weeks, or about 2.3 months, premature. Assessed at a chronological age of four months, the corrected age is roughly 1.7 months, and milestones should be expected accordingly. Correction is applied until about 24 months of age, after which chronological age is generally used. A baby born at full term carries no correction at all.