Prematurity and “Corrected Age”: How Old is Your Preemie

September 9, 2022

I'm katie, OTD, OTR/L, NTMTC, CNT & founder of blooming littles

Guess who has the greatest influence on a baby's NICU stay? It's YOU! Let's get you the tools, info, and resources needed to create positive NICU experiences, one interaction at a time.

Need help understanding or teaching on NICU baby cues?

download it!

Download our NICU cues workbook and become a cue-based caregiving champion!

So, your baby was born at 26 weeks estimated gestational age (EGA), but they’re 4 weeks old chronological age, which makes them 30 weeks postmenstrual age (PMA). Now when she’s two weeks past her due date, she’ll be two weeks corrected age????.”


Don’t worry if you didn’t understand a word of that. We’re going to break it down in this blog post so you can reference it whenever you need to.

You’re not alone if you’ve ever been confused by the term “corrected age”, or the statement, “make sure to adjust for prematurity”. 

Let’s talk about what each of these NICU ages mean, when you should use them, and why they’re so important.


A baby is formally considered premature if they were born before 37 weeks gestation. Babies born between 32-37 weeks are considered late preterm, and babies born before 32 weeks are very or extremely premature. 

Several of the terms we’ll talk about in this post, including “corrected age”, are used specifically for preemies—babies born before 37 weeks. 

If your baby was born after 37 weeks, you will use their chronological age (the way we always calculate age).

There are actually some specific ways that preemies develop differently from term babies. You can learn more here.


The NICU has a lot of terms to learn. Here is a breakdown of some of the most common ages you could hear on your NICU journey. 

Estimated Gestational Age (EGA)

This is the age of a pregnancy. It’s the number used to describe the age of your baby at birth. For example, if your baby was born premature at 29 weeks and 3 days, then their EGA at birth would be 29 weeks and 3 days. 

Postmenstrual Age (PMA)

PMA is used to describe the age of premature babies BEFORE they reach their due date. 

For example, your premature baby who was born at 29 weeks and 3 days (now 2 weeks old) would have a PMA of 31 weeks and 3 days.

Once a baby reaches their due date, we generally stop using PMA.

Corrected Age/Adjusted age

Corrected age is used for premature babies AFTER they reach their due date when looking at how they are progressing through developmental skills.

For example, if your baby was born at 29 weeks EGA, and they’re 4 months old (16 weeks), then they are 5 weeks corrected age. 16-11=5!

Chronological age

Chronological age is used to describe the current age of your baby without adjusting for prematurity.

For example, if your baby was born at 29 weeks and 3 days, and they’re 4 months old, their chronological age is 4 months.

click the image above to learn more on the @bloominglittles instagram


If you’re wondering whether your baby is “on track” developmentally, you are going to use their corrected age (sometimes called adjusted age). 

If your baby was born premature and you’re wondering when they should be rolling over or sitting up on their own, use their corrected age when comparing their skills with developmental milestone charts.

Now, let me share why that’s important.


It’s important to use corrected age when looking at how your baby is progressing developmentally because we don’t want to count those months your baby was born prematurely against them. 

If your baby was born 3 months early, as a 3 month old, they should only be behaving and meeting the skills of a newborn.

It wouldn’t be appropriate for their immature and developing nervous and motor systems to do the more advanced skills of a 3 month old baby, like rolling to their side or batting at toys. 


There are a couple of different ways to calculate your baby’s corrected age. 

Option 1: Begin with your baby’s actual age in weeks (number of weeks since the date of birth) and then subtract the number of weeks your baby was preterm.

Option 2: If your baby has passed their due date, you can simply count the number of weeks/months from their due date, instead of birth date. 


Corrected age can be used to account for your baby’s prematurity until they are 2 years old. At that point, it’s been determined that many preemies have “caught up” with their peers and adjusting for prematurity is no longer necessary.

This doesn’t mean your baby will need that extra time to catch up on milestones, but there may be some areas of development that match their corrected age and others that match their chronological age. 

Every baby grows and develops at their own pace!

Remember: Age isn’t everything. We use it as a guide to help us understand medical, growth and neurodevelopmental progress. 

It can be SO easy to get caught up in “when” your baby is meeting milestones and whether they’re behind. Celebrate EVERY. SINGLE. GOOD. THING. 

Nothing is too small to celebrate. Every smile. Every coo. Every toy touched. Every step taken. 

Your preemie is a miracle. I always tell parents I’m working with to look at overall progress. Is your baby learning new things? Amazing! Let’s focus on that. It’s worth celebrating the skill and how far they have come…not the day and age it happened.

Have you noticed they haven’t really done anything new in a while? Or maybe plateaued in their skills? It may be time to bring up concerns to your pediatrician or seek out some early intervention therapy services. 

Looking for a good resource? Pathways.org is an incredible resource as you learn more about development after NICU discharge. 

There’s a lot to worry about when you have a baby in the NICU. If you find yourself discharged home, working on a routine. Just BE. Be with your baby. 

Snuggle them, feed them, stare at them. Enjoy the stillness, sweet friend. 

The hustle and bustle will come. Enjoy your miracle.

explore more popular NICU posts...

How developmentally supportive is your NICU practice?

free worksheet

©2024 all rights reserved. BLOOMING LITTLES® | Design by Tonic  |  BRANDING By CEMBER STUDIO |  privacy policy  | terms & conditions    


SEND us A message>


at blooming littles, we believe every baby was born to bloom.