Finding Balance: Rethinking Growth Goals for Preterm Infants

For decades, doctors caring for very preterm babies have wrestled with a tough question: What does “good growth” really look like outside the womb?

Traditional goals often push for preterm babies to grow as though they were still in utero, and to look like full-term newborns by the time they leave the hospital. But these idealistic expectations can be stressful for both families and clinicians, especially when they prove unrealistic.

Our new multicenter study, “Association between Growth Trajectories and Body Composition Outcomes in Very Preterm Infants,” sheds light on this challenge. By examining over 1,000 infants born before 32 weeks across the U.S., Canada, Germany, and Austria, we tested whether setting more realistic, individualized growth goals could give us a better picture of how preterm babies develop.

From Growth Curves to Growth Trajectories

Instead of relying only on traditional growth charts, the study used the growth calculator (www.growthcalculator.org). This tool takes into account natural early weight loss in preterm infants and generates a personalized “trajectory” for each baby, from birth to the time they reach term-equivalent age.

Infants were grouped into three paths:

Below target (≥100g under their individualized goal)
Within target (±99g of their goal)
Above target (≥100g over their goal)

This approach helped move beyond a one-size-fits-all standard to capture each baby’s unique growth pattern.

What tWe Found

The results showed a clear link between growth trajectories and body composition outcomes:

Infants below target had lower fat-free mass (FFM) z-scores, meaning less muscle and lean tissue, and experienced greater declines in weight, length, and head circumference.
Infants within target had healthier balances of lean tissue and body fat, even though their growth still did not fully match that of full-term peers.
Body fat percentages varied significantly depending on gestational and postnatal age, underscoring that growth isn’t linear, and shouldn’t be expected to be.

In other words, staying within an individualized growth target seemed to support better overall body composition, even if absolute growth measurements fell short of traditional “ideal” goals.

Why This Matters

Lean tissue growth (FFM) is thought to play a critical role in long-term neurodevelopmental outcomes. By focusing only on weight, clinicians may miss whether babies are gaining the “right” kind of tissue. This study suggests that monitoring individualized trajectories could be a more meaningful way to guide nutrition and track growth.

And perhaps equally important: setting realistic goals could relieve some of the pressure families and providers feel when preterm babies don’t fit traditional standards.

The Road Ahead

This work isn’t the final word. Because only infants with body composition measurements were included, sicker babies weren’t represented. The lack of detailed nutrition data also limits how widely the findings can be applied. Still, the study lays important groundwork for larger, prospective, longitudinal trials.

Future research will test whether tracking growth trajectories in real time through weekly assessments can help clinicians make better nutrition decisions and improve outcomes for preterm infants.

Bottom line: Growth in preterm infants is not about chasing perfection. It’s about finding balance, supporting babies to achieve the best growth they can, with an eye toward quality, not just quantity.