What it is
Corrected (or adjusted) age accounts for the weeks a preterm infant missed in utero, so growth and development are judged against where the baby would be had they reached term. Without it, a baby born two months early looks “delayed” against chronological-age milestones when they are in fact on track for their corrected age.
The method
Two simple steps:
- Weeks of prematurity = 40 − gestational age at birth (in weeks).
- Corrected age = chronological age − weeks of prematurity.
No correction is applied for term or post-term birth (the subtraction floors at zero). Distinguish corrected age from postmenstrual age (PMA = gestational age at birth + chronological age), which is used in the neonatal unit; corrected age is the outpatient/follow-up term.
When to use it
Use corrected age for any infant born < 37 weeks when assessing:
- Growth — plot on the growth chart at corrected age (or use a preterm chart such as Fenton until term-equivalent).
- Developmental milestones and neurodevelopmental screening.
- Timing of routine assessments and some interventions.
Conventionally correct until about 2 years of age; for very preterm infants many follow-up programmes continue correcting to 3 years. Note that immunisations are given by chronological age, not corrected age — do not delay them.
Worked example
A baby born at 32 weeks, now 16 weeks (4 months) old:
- Weeks of prematurity = 40 − 32 = 8 weeks.
- Corrected age = 16 − 8 = 8 weeks ≈ 2 months.
So this 4-month-old chronologically is assessed against 2-month milestones — social smile and beginning head control, not rolling. Judging them at 4 months would falsely flag a delay.
Pitfalls and caveats
- A negative corrected age simply means the infant has not yet reached term-equivalent (40 weeks PMA) — expected for a baby still young in the neonatal period.
- Don’t mix up corrected age and PMA — PMA counts from the last menstrual period and is the NICU currency; corrected age counts from term and is the follow-up currency.
- Immunisations and some screening (e.g. ROP) follow chronological/postmenstrual schedules, not corrected age — correcting these would be an error.
- Stopping correction too abruptly at 2 years can create an apparent “drop” in milestone status; transition with judgement, and keep correcting longer in the very preterm.
Run it: Corrected (Adjusted) Age for Prematurity
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.