Corrected age and catch-up growth in the preterm infant

What it is

For prematurity, each measurement is corrected for a different length of time: weight corrections are needed until 24 months of age, height corrections until 40 months of age, and head circumference corrections until 18 months of age. How long the correction runs depends on how early the birth was: corrected age is used until 1 year if the baby was born at 32 to 36+6 weeks, and until 2 years if born before 32 weeks. What the age is used for matters as much as how long. For development and growth use the corrected age; for vaccination use the chronological age. So a 9 month old ex-preterm whose corrected age is 6 months has his development read at 6 months and his vaccines given at 9 months.