Aubrey Phelps MS RDN CLC
“Catch-up growth.”
It’s a term that most parents have never even heard, but parents of preemies and babies born smaller than their peers probably feel like they hear every appointment. So what is catch-up growth? And more importantly, what isn’t it?
Like many ideas in the medical world, “catch-up growth” is often discussed as if it is an agreed upon phenomenon and expectation. In reality, “catch-up growth” is poorly defined, inconsistently described from one facility to another, and varies from country-to-country. The original term of “catch-up growth” was used to describe a period of rapid linear growth after a period of illness. It was applied to an observed phenomenon of children recovering from starvation or illness who have height growth that was above the normal velocity when the period of inadequate nutrition ended. In other words, “catch-up growth” isn’t something that was originally a goal, but instead is something some children just naturally did after temporary periods of weight loss.
However, at some point, this notion of rapid growth that many children did spontaneously was applied to preterm and low birth weight/growth restricted infants. While the idea that these individuals might exhibit “catch-up growth” wasn’t a bad one, ultimately, the idea was incorrectly applied and taken too far. Working backwards, medical professionals and researchers determined an equation that described the calories needed to accomplish this type of increased growth velocity, and in doing so, “catch-up growth” became a “prescription” instead of a calculation.
But this is a misunderstanding of what “catch-up growth” actually is: growth that some children just do, all on their own, and not growth that can be prescribed or expected of all children.
What does this mean, practically speaking?
It means that in the same way we can calculate the number of calories a person should consume to lose a pound of weight, we can also calculate the amount of calories a child would need to consume to “catch-up” to a particular percentile. But that doesn’t mean I can, or should, make that their actual goal!
It means that, for tube-fed children, it’s easy to use that “catch-up growth” calculation as their calorie goal, but in practice, this often results in poor feeding tolerance, overfed fussy babies, who spit up and vomit excessively. It can also create disproportionate growth, where children gain weight at an increased velocity, but we see little to no increase in their length or head circumference growth. This means that, just because a child is getting more calories doesn’t mean that they are growing in length or head circumference, even if they gain weight.
For oral children, it means that prescribed calories are a bit absurd. Frankly put, we rarely and only in unique circumstance, give fluid or calorie goals to oral children. Instead, we might assess their current calorie intake and how that compares to the calculation for “catch-up growth” needs, but no one can “make” children consume more calories than their bodies need. And no one is dropping a tube in every child born small or premature just to force “catch-up growth” calories into their bodies.
In other words, there are thousands of small, growth restricted children out there who aren’t tube fed and who aren’t hitting that “catch-up growth” calculation because while small, they are happy, healthy and growing on their curve.
It also means that children who are growing at an accelerated rate due to increased calories through the tube may deviate from that growth pattern when they become typical oral eaters. That doesn’t mean they’re not healthy, and it doesn’t mean they won’t grow well. It also doesn’t mean that they won’t “catch-up,” if that’s even something then really need to do (examining whether catch up growth should even be a goal is a topic for another time!)!
While it can be so hard to see your child’s growth curve change post-wean, especially when you’ve worked so hard to get them up to a certain point and heard over and over that they “need” to grow a certain way, the reality is that weight gain is only one way to asses how a child is progressing. And while it’s hard to break that medical mindset that fixates on calories, ounces, grams gained per day, etc., making that adjustment can highlight the other ways your child is growing (length, developmental milestones, new vocabulary, skill development, etc.)
Just as it’s been observed in the actual literature, some children naturally choose to eat in a way that accomplishes what we now term “catch-up growth,” but some don’t! And we definitely don’t have a consensus or even good research on whether “catch-up growth” is correlated with better overall health outcomes for children. So, while it might be helpful to know how much your child would need to eat/consume in order to increase their growth velocity, think of that data as another data point, rather than an actual prescription of what to do.