Why a preemie's birthday can lie about their milestones

If your baby arrived early, comparing them to a full-term calendar can spark needless worry. That's where corrected age (also called adjusted age) comes in: you subtract the number of weeks or months your baby was born early from their actual age on the calendar. A baby born 2 months premature who is 6 months old by the calendar has a corrected age of about 4 months — and that's the age their development should be measured against.

Here's why it's fair: a baby born at 32 weeks simply hasn't had as much time to grow, move, and practice as one born at 40 weeks. Judging them by their birth date is like grading two students on the same test when one started the course two months late. Most experts adjust for prematurity until around age 2, by which point the gap typically evens out for many children.

So a preemie who isn't yet rolling at 6 calendar months may be right on time at a 4-month corrected age. This small math trick reframes 'behind' as 'exactly where they should be' — and helps you and your pediatrician track real progress rather than false alarms.