Corrected gestational age for premature babies
8-minute read
Key facts
- ‘Corrected age’ is your baby’s age after accounting for how many weeks or months they were born premature.
- ‘Chronological age’ is how many weeks or months since your baby was born.
- ‘Corrected age’ is used to monitor that your baby’s growth and development is on track. It also helps your health team decide when you can start giving them solid foods.
- The timing of routine vaccinations is usually not changed for prematurity.
What is corrected age?
Your baby’s corrected age is the age your baby would be if they had been born on their due date, instead of being born premature. For example, if your baby was born 3 months early and it is now 7 months from your baby’s birth, your baby’s corrected age is 7 months minus 3 months, giving a corrected age of 4 months.
What is chronological age?
Your baby’s chronological age is how many weeks or months have passed since your baby was born. It does not include how many weeks premature they were.
How do I work out my baby’s corrected age?
During your baby’s time in the nursery, the staff will calculate your baby’s corrected age each day. If your baby hasn’t yet reached their due date, their corrected age is calculated by adding how many days or weeks old they are, to the number of weeks and days you were pregnant when your baby was born. For example, if your baby was born at 32 weeks and 1 day of pregnancy and your baby was born 3 weeks ago, your baby has a corrected age of 35 weeks and 1 day.
How to calculate your baby’s corrected age
You can calculate your baby’s corrected age by subtracting how many weeks premature they were born from their actual age (how many weeks since they were born).
Chronological age – how many weeks premature = Corrected age
For example, if you baby’s chronological age is 16 weeks (they were born 16 weeks ago) and they were 8 weeks premature, there corrected age is 8 weeks.
16 weeks old – 8 weeks premature = 8 weeks corrected age
Why is my baby’s age corrected?
Corrected age is used to help your health team check your baby’s growth and development, while taking into account your baby’s prematurity. For example, a baby born on its due date who is 3 months old, and a baby born at 28 weeks and is 3 months old, would not be expected to be at the same developmental stage. Premature babies need some time to catch up.
Even if you are using a corrected age, the date you celebrate your baby’s birthday doesn’t change.
When does corrected age stop being used?
Your baby’s corrected age will usually stop being used after 2 to 3 years of age.
Can prematurity affect my baby’s growth, development and health?
Most premature babies go on to develop like babies born at term. But the earlier that premature babies are born, the more likely it is that they’ll have development problems. In general, it would not be expected that a premature baby will be at the same developmental stage as a baby born at term. This is because premature babies need some time to catch up, particularly in the early months and years after their birth.
If you baby is born early, they can experience a variety of health problems. These problems may include the following:
- Breathing difficulties, including pauses in breathing (apnoeas), scarring of the lungs, or respiratory distress syndrome — when your baby’s lungs don’t have enough fluid (surfactant) to keep the small air sacs open.
- Feeding difficulties can include trouble coordinating sucking, swallowing and breathing. You can still give your baby the benefits of breast milk by expressing and feeding them through a tube or another aid. Your health team will help you do this.
- Infection can be due to your baby having an immature immune system, and being exposed to infections in hospital or before birth.
- Jaundice is when your baby’s liver hasn’t developed enough to clear waste products.
- Neurological problems include cerebral palsy, developmental delay, behavioural problems and autism spectrum disorder. Cognitive delay is usually more severe the more premature your baby was born.
- Other problems include vision problems (retinopathy of prematurity), bleeding in the brain (intraventricular haemorrhage), or serious bowel problems (necrotising enterocolitis).
When should my baby have their vaccinations?
If your baby is well enough, they should have their vaccinations according to the National Immunisation Program schedule for their chronological age, not corrected age. Immunisation is especially important for your baby, as being premature means their immune system is less developed and your baby may be at higher risk of vaccine-preventable illnesses. Premature babies usually tolerate vaccinations well, but sometimes have breathing pauses (apnoeas), which usually settle by themselves. Your health team will monitor your baby for these in hospital.
Your baby might need an extra dose of some vaccines, for example the hepatitis B vaccine, since being premature may make their immune response to the vaccine not as strong. The extra dose gives them long lasting protection from the disease. Your medical team will discuss its recommendations for your baby with you.
When should my baby start solids?
Your baby can usually start solids at a corrected age of 3 months or a chronological age of 5 to 7 months. It’s important to start solids by 7 months chronological age to balance your baby’s chances of developing allergies, their willingness to try new foods and their nutritional needs.
The exact timing will depend on how early your baby was born and how they are developing. Speak to your doctor or child health nurse about when to start solids based on your baby’s individual needs.
Signs that your baby is ready to start solids
- Your baby can sit supported on your lap or in a high chair.
- Your baby can hold their head in one position.
- Your baby often puts their hands or toys in their mouth.
- Your baby leads toward food and opens their mouth when you offer them food.
When should I see a doctor?
If your baby spends time in a special care (SCN) or intensive care nursery (NICU), you will have a follow-up visit with a paediatrician before you take your baby home.
You should see a doctor for your baby’s routine vaccinations and check-ups.
You should also see a doctor more urgently if your baby is not feeding well, not waking up for feeds, having trouble breathing, making less than half of their usual number of wet nappies, has a fever, or if you are worried.
Whenever you take your baby to any health professional, let them know that your baby was born premature.
Resources and support
- To calculate your baby’s corrected age, see this online calculator. Be sure that you are using the same due date as your health team, so that you calculate the same corrected age.
- Read more about feeding your premature baby and introducing solids from the The Royal Women’s Hospital
- If you need support after having a premature baby, Miracle Babies Foundation has online resources and a 24 hour support line — call 1300 622 243.
Speak to a maternal child health nurse
Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.