Preemie Growth Chart Basics


If you are the parent of a premature infant, you may be wondering what to expect after delivering preterm. Perhaps you are also wondering how your baby compares on the growth chart to babies born full term. If so, you’re not alone. The World Health Organization (WHO) estimates more than 1 in 10 babies worldwide are born earlier than 37 weeks, or preterm. That’s why we’ve laid out the preemie growth chart basics to help guide you through the process.

There are allowances made to the growth chart and developmental milestones for premature (preemie) babies.

Did you know that the MonBaby sleep monitor helps parents track breathing movements and sleep position for preemies and high-risk babies? See it here: MonBaby Smart Button

Newborn baby measurements

Once a full-term baby is born, he/she will be measured and compared on a growth chart with other full-term babies. Typical measurements taken are weight, length, and head circumference.

  • Birth weight signifies a lot about a newborn baby’s health. The average weight for full-term babies is 7 pounds (3.2 kg). Your baby will be weighed at every checkup to assess growth.
  • Length is measured from the top of the head to the heel of one foot, averaging 50 cm (19.54 inches) long.
  • Head circumference is the distance around the largest part of the baby’s head, averaging 13 ¾ in (35 cm). Deviations from the normal range could indicate problems in brain development.

The preemie growth chart is different

Premature babies are measured a little bit differently. Physicians will ‘adjust’ the baby’s age to get a more accurate understanding of how he/she is developing. This is called the ‘adjusted age’.

This is how it works:

If your baby is 16 weeks old but was born 4 weeks early, subtract 4 from 16. 12 weeks is the adjusted age, and 12 week milestones are what your baby should be achieving. By age 2, and quite possibly sooner, your preemie baby should be caught up and you won’t have to adjust his/her age.

Try to be patient with your sweet little one. It would be unrealistic to expect your 4-month-old baby to be doing the same things as another 4-month-old if she spent the first 2 months fighting for her life in the NICU.

What does a growth chart look like?

At checkups, your baby’s pediatrician will most likely provide a chart that looks like a graph with a curve, which represents average growth patterns. A dot represents where your baby falls in comparison with infants of the same age. If the dot is below the ‘average’ line, your baby measures lower than average in growth. If above the ‘average’ line, your baby measures higher than average in growth.

Your preemie growth chart will show your baby’s rank as a percentile. For example, if your 12-week-old boy ranks in the 30th percentile for weight, he weighs the same or more than 30 percent of the reference population of 12-week-old boys. (Remember to use the adjusted age when measuring preemies.

What determines growth rates?

Three factors influence all children’s growth:

  1. Nutrient intake – What your child eats and drinks
  2. Genetics – Inheritable disorders
  3. Environmental circumstances – Medication, biological influences, disease

While you don’t have control over the genetics you pass on to your baby, try to provide the best nutrient intake and environmental circumstances for your infant to contribute to healthy growth.

Taking care of a baby is difficult, but remember you don’t have to know all the answers. There are physicians, teachers, literature, and more available to help you and your baby every step of the way. It’s important to remember that each child develops differently; giving your love, support, and affection is what your baby needs most.

To learn more about caring for your premature baby, visit our Preemies section.


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