What Is Corrected Age (Adjusted Age)?
When a baby is born prematurely, their brain, body, and development reflects the stage of gestation — not the calendar date. Corrected age accounts for this by calculating age from the original due date (40 weeks), not the actual birth date.
Formula: Corrected Age = Chronological Age − (40 − Gestational Age at Birth)
Example: A baby born at 28 weeks is 12 weeks (3 months) premature. At 6 months chronological age, their corrected age is 6 − 3 = 3 months. On a WHO growth chart, you would plot them at 3 months, not 6 months.
Why Corrected Age Matters for Growth Charts
Without correction, a premature baby at 6 months would appear dramatically underweight and short on a growth chart — even if they are perfectly healthy and growing exactly as expected for their biological age. This can cause unnecessary parental anxiety and inappropriate medical interventions.
Using corrected age puts the baby's growth in the right context and gives parents and clinicians an accurate picture of development.
When to Stop Using Corrected Age
| Domain | Stop correcting at |
|---|---|
| Growth monitoring (height, weight, head) | 24 months chronological age |
| Developmental milestones | 24 months (varies by milestone) |
| Cognitive/social development | 36–48 months for very preterm (<28wk) |
Frequently Asked Questions
What is corrected age for a premature baby?
My baby was born at 34 weeks. How premature is that?
Does catch-up growth always happen?
Track your preemie's growth with corrected age built-in
GrowChart automatically applies corrected age for preterm babies throughout the app — no manual calculation needed. Growth charts, z-scores, and alerts all use the right age.