The Difference Between Corrected Age and Chronological Age—and Other Answers to Your Preemie Baby Development Questions

Whether this is your first or fourth child, a new baby is always exciting. And when you have a premature baby—one born more than 3 weeks early—you can expect to have more questions about his development than parents of a full-term infant.

Keep this in mind: each baby (your preemie included) will develop at his own speed and in his own way. Milestones of growth are reached at each baby’s own pace. Since your preemie may have a bit more catching up to do, this may leave you wanting answers to questions not all parents think about.

After coming home from the hospital, your preemie may be catching up on time lost in the womb by growing and developing fast, but maybe not as fast as you expect. His development will likely be delayed by the same number of weeks he was prematurely born.

For example, if your preemie was born 8 weeks early, he can be expected to develop about 8 weeks behind babies born at full term. Keep this in mind when it comes to feedings, introduction of baby foods, and your pediatrician sharing those first baby measurements with you. A pediatrician appointment is the perfect time to bring up any concerns you might have about your baby.  

It’s recommended that you track your baby’s progress at home over the first few months. It can help spark discussions about your preemie’s growth and development with your pediatrician. The Similac^® NeoSure^® Milestone Tracker(PDF, 0.25 MB) can help.

How old is your baby, really? The fact is, your premature baby has two ages:

• The age from his actual birth is his chronological age
• The age based on his original due date is his corrected age. Also called adjusted age, this is the age difference between when he was due and when he was actually delivered. For example, a 10-week-old who was born 8 weeks early would have a “corrected” age of 2 weeks

Why is this important? Because your preemie might reach milestones in development at a pace closer to his corrected age than his chronological age. Knowing both will help you and your doctor better track his development. To track your preemie’s growth compared to full-term babies, it is recommended his doctor track his corrected age for his first year or more.  

The Similac NeoSure Corrected Age Calculator(PDF, 0.75 MB) will make it easier to remember your baby’s corrected age.

Since preemies start smaller, they need to grow faster than usual to become the same size as a full-term baby. This is called "catch-up growth." Many preemies will catch up on their growth by about 12 to 18 months of age.^* 

Whether you choose to breastfeed or use baby formula after leaving the hospital, your premature baby may require extra help to grow throughout the first year. Your preemie is working hard to grow and develop, and supplementing with a nutrient-enriched,^† preterm, post-discharge formula like Similac NeoSure can help. It’s designed to support brain, eye, muscle, and bone growth, as well as baby’s immune system.

Shop and learn more about Similac NeoSure.

Tracking these growth changes in your preemie can prompt important conversations with your pediatrician. You can track your baby’s progress with the Similac NeoSure Catch-Up Growth tracker(PDF, 0.80 MB).

Neonatal intensive care units (NICUs) are well-equipped and staffed to constantly monitor, feed, and care for premature babies. Because this care often happens in an incubator (the clear, enclosed crib your baby may have spent time in at the NICU) and because premature babies require less stimulation than babies born at term, a preemie’s physical needs are met in ways that are different from term-born babies.

To make sure your baby is still being supported by positive physical experiences, your nurses or doctor might recommend "kangaroo care" for you and your preemie.  

Kangaroo care encourages the skin-to-skin contact that has benefits for both parent and baby. It helps regulate his temperature, and research shows a mother’s scent and voice have a calming and comforting effect that aids in baby’s development. 

Kangaroo care is simple to learn. It’s not only rewarding for your preemie, but also comforting for parents.  

The kangaroo position provides your little one with all kinds of positive stimulation needed for development, which includes:

• Hearing, through the sound of your voice
• Smell, though closeness to your body
• Touch, through skin-to-skin contact

It’s easy for parents. Here’s a quick how-to:

1. Find a comfortable seat. Lay your baby—dressed only in a diaper and a hat—on your bare chest. 
2. Turn his head to one side so that his ear rests slightly above your heart. Use a soft sheet, robe, or your shirt to cover your baby. 
3. Keep your preemie’s head upright and uncovered, except for hat, to allow for unrestricted breathing.
   

If possible, keep your little one in the kangaroo position for at least an hour, so one complete sleep cycle occurs. You may find kangaroo care offers a wonderful bonding experience!

* Your preterm baby may grow faster or slower than this. Work with your baby’s pediatrician to understand what’s best for your baby.
^† Increased protein, vitamins, and minerals compared to term infant formula.