What is corrected age?
When a baby is born prematurely, their body and brain missed some of the development time they would have had in the womb. Corrected age (also called adjusted age) accounts for that by counting age from the due date instead of the birth date.
The formula is simple:
Corrected age = chronological age − weeks born early, where weeks born early = 40 weeks − gestational age at birth.
For example, a baby born at 32 weeks arrived 8 weeks early. When that baby is 6 months old on the calendar, their corrected age is about 4 months — and 4-month milestones, not 6-month milestones, are the fair benchmark.
Why corrected age matters
- Milestones — rolling, sitting, babbling and walking should be expected at the corrected age, not the chronological age. Comparing a preemie against full-term timelines causes unnecessary worry.
- Growth charts — pediatricians often plot preterm infants by corrected age in the first year or two.
- Developmental assessments — many screening tools instruct examiners to use corrected age for children born preterm, typically up to 24 months.
How long is corrected age used?
Most guidance uses corrected age until about 24 months of chronological age. By then, the gap between a preemie and full-term peers has usually narrowed enough that correction is no longer needed. Some specialists extend it for very early births — follow your own pediatrician's advice.
Frequently asked questions
My baby was born at 36 weeks. Do I still correct?
Babies born between 34 and 36 weeks ("late preterm") are still preterm, and correction of a few weeks can matter for early milestones. Babies born at 37 weeks or later are considered term and do not need correction.
Which age do I tell people when they ask?
Chronological age is the everyday answer ("she's six months old"). Corrected age is the developmental answer used with doctors and therapists. Many parents keep both in mind during the first two years.
Is the due date shown here exact?
It is an estimate calculated as birth date + (280 days − gestational age at birth in days). Your actual clinical due date may differ slightly; you can rely on the one from your medical records.