Understanding your babies' adjusted or corrected age

Why premature babies may have more than one age

Medical professionals use a lot of terminology, which can feel overwhelming when you already have a lot on your mind. If you had complications in pregnancy or your babies were born early, you may hear new phrases and abbreviations at every appointment.

One of the most common ideas to get used to is that your premature babies may have two ages. These are called their actual age and their corrected, or adjusted, age. Understanding the difference can really help when you’re thinking about developmental stages and what feels normal for your children.

Babies born before 37 weeks of pregnancy are classed as preterm. Twins born after 37 weeks will usually only be given an actual age because they arrived close to their due date. Triplets or quads are almost always born before 37 weeks, so they’re usually given both an actual age and a corrected, or adjusted, age.

How to work out your babies’ corrected age

Your babies’ actual age is simply how long it’s been since they were born. Corrected or adjusted age takes into account how early they arrived. It gives a clearer picture of where they might be on their developmental journey.

To work it out, you look at how many weeks before 40 weeks’ gestation your babies were born. You then subtract that number of weeks from their actual age.

For example, if your triplets were born at 32 weeks, they were born eight weeks early. When they reach four months, or about 16 weeks, of actual age, you subtract eight weeks. Their corrected age would be around two months. This means it’s completely expected for them to show the skills linked to a two-month old rather than a four-month one. It is also worth noting that some premature babies track with their actual age even though they have a corrected age so it's important to treat each baby individually.

You might find it helpful to jot this down in your phone or on a calendar so you can quickly remind yourself of both ages. Some parents like to think in terms of ‘they’re four months old, but two months corrected’. Others prefer to use the corrected age only when they’re thinking about developmental stages.

Using corrected age for developmental stages, sleep and routines

Corrected age is particularly useful when you’re looking at developmental stages. Books, apps and baby groups often talk about what babies ‘should’ be doing at certain ages. This can feel stressful when you’re caring for twins, triplets or more who arrived early.

If your babies are four months old in actual age but were born eight weeks early, it’s normal for them to be in the developmental stage of a two-month-old. They may reach skills like smiling, rolling, sitting or babbling later than babies born at full term. This doesn’t mean they’re behind. It usually means their development is following their corrected age rather than their actual age.

Corrected age is especially helpful when you’re thinking about sleep needs and routines in the first year. Premature babies may need different amounts of sleep or take longer to move towards more predictable patterns. Looking at their corrected age can make expectations feel more realistic and reduce pressure on you.

It’s also important to remember that all children develop at different rates. Even within the same family, each of your babies will move through developmental stages in their own time. One may talk earlier, another may walk earlier and another may take the lead with social or problem-solving skills.

If you’re unsure about what to expect at different ages, your health visiting team can talk this through with you. Resources such as the Early Years Alliance parents guides - from the Early Years Foundation Stage - can also give a broad picture of developmental norms for children under five.

Getting support if you’re worried about development

You’re with your babies more than anyone else, so you’re best placed to notice small changes over time. If something doesn’t feel right, or you’re worried about how any of your twins, triplets or more are developing, it’s always OK to ask for help.

Start with your health visitor, GP or neonatal follow-up team if you have one. You can ask them to explain actual and corrected age again and to help you understand what this means for your babies right now. If needed, they can arrange extra checks or refer you to other services.

Twins Trust’s play booklet (LINK) includes general guidance on what you might see at different ages. For premature babies under two, it’s helpful to read this alongside their corrected age so expectations feel more realistic and reassuring.

If you ever feel dismissed, or you still feel uneasy after an appointment, it’s OK to go back and ask more questions. You’re advocating for your children, and professionals are there to support you. Together, using both actual and corrected age, you can build a clearer picture of how your babies are growing and what support they might need.