vitababyIn short
Premature babies are tracked using corrected age (also called adjusted age): you subtract the number of weeks they were born early from their actual age, so growth is compared to when they were due rather than when they were born. In the UK, preterm babies are plotted on the neonatal and infant close monitoring (NICM) chart and then the UK-WHO charts using corrected age, usually up to around age two. Many premature babies show catch-up growth over the first year or two — your neonatal team and health visitor will guide how your baby’s growth is followed.
Key takeaways
- Premature babies are tracked using corrected (adjusted) age, based on their due date.
- Corrected age = actual age minus the number of weeks born early.
- UK preterm babies use the NICM chart and then UK-WHO charts plotted by corrected age.
- Catch-up growth over the first year or two is common; the neonatal team and health visitor guide monitoring.
What corrected age means
Corrected age (or adjusted age) accounts for being born early. It compares your baby’s growth and development to when they were due to be born, rather than their birth date. This gives a fairer picture, because a baby born two months early would not be expected to be the same size or stage as a baby of the same birth-age who was born at term.
How to work it out
To find corrected age, subtract the number of weeks your baby was born early from their actual age. A baby born at 32 weeks is eight weeks early; at four months of actual age, their corrected age is two months. Weight and progress are judged against that corrected age. Corrected age is usually used until around two years old, after which the difference becomes small.
- Corrected age = actual age − weeks born early.
- Example: born 8 weeks early, actual age 4 months → corrected age 2 months.
- Corrected age is typically used up to around age two.
Which charts are used in the UK
In the UK, very premature babies are first plotted on the neonatal and infant close monitoring (NICM) chart, then move to the standard UK-WHO growth charts with weight plotted at corrected age. Your neonatal unit and health visitor will explain which chart your baby is on and how often they will be weighed, which is often more frequent at first.
Catch-up growth and when to ask
Many premature babies show catch-up growth over the first one to two years, moving towards their own steady centile. Growth may be monitored more closely than for a term baby. Speak to your health visitor, GP, or neonatal team if your baby’s weight gain stalls, they are feeding poorly, or you are worried — premature babies sometimes have extra feeding or nutritional needs that the team can advise on.
VitaBaby lets you record weights and feeds and view the trend, which you can bring alongside the corrected-age charts your neonatal team and health visitor use.
FAQ
How do I calculate my premature baby’s corrected age?
Subtract the number of weeks your baby was born early from their actual age. For example, a baby born eight weeks early who is four months old has a corrected age of two months. Growth is judged against the corrected age.
How long do you use corrected age for?
Corrected age is generally used until around two years old. By then the difference between corrected and actual age has a much smaller effect on growth and development.
Do premature babies catch up in weight?
Many premature babies show catch-up growth over the first year or two and settle onto their own centile. Growth is often monitored more closely; your neonatal team and health visitor will guide this and flag if extra support is needed.
Sources
- Growth charts — Royal College of Paediatrics and Child Health
- Information and support for parents of premature and sick babies — Bliss