Skip to Content

Understanding the Corrected Age of a Premature Baby

Understanding the Corrected Age of a Premature Baby

Having a preemie uncovers a whole new world! And, among the first things that we preemie parents have to understand is how our baby’s corrected age works.

This was a challenge I honestly didn’t know I was going to have. It all came down to knowing why my son needed two ages and when to use which one.

After all, adjusted age is there to give our baby’s a break. When they are born, they have to catch up with breathing, seeing, hearing, developing their lungs, digestive systems, hearts… On top of that, we can’t force them to meet milestones at the same time as full-term babies.

That’s where the corrected age comes to the rescue!

In this post, I’m breaking down the basics of a preemie’s adjusted age, so that you can easily manage your child’s development.

Are you a preemie mom? Here's how adjusted age (or corrected age) works and how to tell your premature baby's adjusted age!

What is Corrected Age (or Adjusted Age)?

For premature babies, who are born any time before 37 weeks of gestation, the due date remains an important milestone.

Oliver, for instance, was born at 31 weeks on May 11th, but his due date was July 13th. Preemies have a lot of catching up to do.

If we didn’t use a corrected age for specific things during their development, they wouldn’t have much of a headstart.

The adjusted age of your preemie is a special age that takes her actual due date and the gestational week into which she was born into account.

How to Calculate Corrected Age?

Corrected Age of a Preemie

I’ve made an adjusted age calculator for my subscribers. To gain access to it, just subscribe to my newsletter (you’ll also receive a complete printable guide to milestones), plus, you can unsubscribe at any time and still have lifetime access to the corrected age calculator.

If you choose to opt-out, no worries!

Calculating your preemie’s adjusted age is very simple. There are two scenarios: Either you are already past your original due date, or not.

If you’re past your due date, just use this formula:

CA = A – (40 – GW)

GW = Number of completed gestational weeks in which she was born.

CA = Baby’s corrected Age in weeks.

A = Baby’s age in weeks.

If your baby still hasn’t reached her due date, then her adjusted age will be measured in gestational weeks. When Oliver was 2 weeks old, his corrected age was 33 weeks of gestation, as if he was still inside the womb.

The formula to calculate the corrected age before your baby’s due date is:

CAgw = GW + A

CAgw = Corrected Age in Gestational Weeks.

A = Age in weeks.

Caution! If your baby’s corrected age in gestational weeks is over 40, then you should refer to the first scenario.

When to use Corrected Age?

Corrected Age of a Preemie

When Assessing Development

It’s what the adjusted age is for! Your preemie has a wider window of opportunity to start reaching milestones.

Preemie’s milestone charts, and development charts, all take into account your preemie’s adjusted age, not her actual age.

Oliver, to give you an example, started eating solids at 6 months old, 4 months adjusted. We decided to wait until he was 4 months adjusted and not chronological because when he was 4 months chronological, his digestive system was that of a 2-month-old. He wasn’t ready.

Even when we started, it was very slow, it took us months before he was actually eating complete meals.

Little by little, you’ll see how she catches up, and she’ll start meeting her chronological age milestones.

For instance, Oliver started walking when he was 17 months old, 15 months corrected. We weren’t worried because he was within the timeframe both for his corrected age and chronological age.

We did, however, over 17 months of Physical Therapy since he was too stiff and stopped moving his arms and legs by the time he was 4 months adjusted. To encourage development, I love Kayla’s post on these top newborn activities, most of them are exactly what we did to solve Ollie’s stiffness, and it worked wonders!

When to Use Chronological Age?

Corrected Age of a Preemie


Your child’s birthdate is the day she was born! No matter her corrected age!

Don’t miss out on a birthday party because you’re waiting for her due date. Eventually, when she catches up, there will be only one age: Her chronological age.


Follow your doctor’s advice on this. But normally the stimulations exercises and techniques are done according to your child’s chronological age.

This way, she’s always aiming to catch up.


If you choose to immunize your child, do it according to her chronological age.

Of course, if your doctor says otherwise, then do as she says. But the general rule is that babies are immunized at their chronological age.

The first time we immunized our son, he was a newborn adjusted (but 2 months chronological.) He was tiny, and we were scared. But he managed, and so did we. And by now his schedule is right on time!

If you need Early Intervention

If you see something that needs special intervention don’t wait for your baby to reach her adjusted age. Act on it.

The earlier you act, the better for everyone!

When Starting School

Oliver started school with his chronological peers.

It’s difficult sometimes seeing the great differences, but we understand that every baby is different. By being surrounded by toddlers the same chronological age that he is, he has thrived and given giant steps developmentally!

When to Stop Using Corrected Age?

There is no consensus here.

It’s true that prematurity goes well beyond NICU, but you should use your child’s adjusted age until it’s relevant for her.

Most people stop using corrected age by the time their preemie is 2 years old adjusted. Since most preemies catch up by this time.

In our case, Oliver is already 2 years old adjusted, but we still need his corrected age at the doctor’s appointments when measuring height and weight.

That’s a Wrap

It may seem complicated, handling two ages. It’s especially difficult when you’re overwhelmed in the NICU, but it becomes second nature to us, preemie parents, after some time.

After all, it’s very convenient. The corrected age gives your child the chance she deserves to catch up with her peers.

Do you have any questions? Let me know in the comments below!


Monday 2nd of March 2020

Thank you for this article. We had a preemie this past January (blessedly only four weeks early, with only 12 days in the hospital). Once out of Special Care, I asked both her pediatrician and the PA when to use corrected v. chronological age, and they refused me a basic breakdown! Now we're seven weeks along and exhausted and I'm wondering - should our expectations around sleep be established using her corrected or her chronological age? Is that considered a "developmental" use of corrected age?


Monday 2nd of March 2020

Hi, Angela!

Thank you for your comment and congratulations on your baby! I'm glad this article helped clear things up a bit!

In my experience, most of the expectations around sleep align with the corrected age in premature babies.

When it comes to sleep, our "newborn phase" lasted for 3 to 4 months (our son was born at 31+6 weeks), and most of the preemie moms I've met have the same experience.

However, I will say that sleep patterns in babies vary greatly from one case to the other, for both full terms and preemies, so it's very difficult to know what to expect in each case.

I'm so happy your hospital stay was short, I'm here if you have any more questions :)




Monday 23rd of July 2018

Wow, crazy to see that your baby way born May 11 with a due date of July 13th, my son was born May 11 2018 with a due date of July 15. We spent 60 days in the NICU and are so happy to finally be home! Thank you for the i formation on corrected age!


Monday 23rd of July 2018

Hi, Carmen!

I'm so happy you found it helpful! Wow, our sons share a birthday (and their due dates!) Thank you for sharing that!

I'm so happy for you, glad that you're all finally at home! The NICU is really a roller coaster. I couldn't wait to be home with my baby, and it was so difficult to see people leave with their babies while staying there, but I'm grateful we had the NICU because my son needed it! So it's conflicting, I'm sure you understand!