Growth Isn’t Linear
Aubrey Phelps MS RDN CLC
Many parents have questions about when to weigh their children while they’re weaning and after they’ve weaned. And while we’ve talked about when to expect weight gain in another post, it’s important for parents to understand why we don’t recommend weighing your child weekly or even monthly, weaning or otherwise.
When your child is very young, under 6 months, we do expect fairly rapid, somewhat linear growth. By that, I mean, that in very young infants, periods of no growth are pretty rare and generally constitute a red flag outside of recently weaning or illness. But, as your child gets older, especially when they hit a year of age and beyond, that pattern of growth begins to change. While you’ve probably gotten used to seeing your child’s curve and how their current measurement compares to their earlier percentiles at each doctor’s visit, in reality, deviating from their curve for brief periods is actually far more “normal” growth than a child that stays constantly at the exact same percentile. In other words, if you’re taking lots and lots of measurements, we’d expect those dots to go both below and potentially above the average curve for your child, rather then trending in a perfectly linear fashion.
Data (cited below) shows that 70% of healthy children had significant shifts in their growth, corresponding with deviations from their overall curve. Instead, children were found to grow in more of a “leaping” fashion consistent with something approximating a series of “mini growth spurts.” These spurts tended to vary in length from about 1-2 months of time, meaning that instead of a child growing incrementally over the course of 30-60 days, they instead of periods of very little growth and then a sudden burst of growth by the end of that period. That means that if measurements are taken too frequently, you’re not going to see the big picture growth taking place. Instead, you’re more likely to catch the interval between these spurts of growth, giving the impression your child hasn’t grown or hasn’t grown “enough,” when in reality, they’re just in the gap between mini growth spurts.
In another study looking at growth from birth to 21 months (also cited below), length growth also occurred in bursts, with children growing anywhere from 0.5 to 2.5 cm during the burst, with then intervals of nearly no measurable growth for up to 2 months! In fact, the data in this study suggests that 90-95% of normal development during the first year or two of life is “growth-free.” In other words, the vast majority of the time, your child isn’t getting taller. Instead, they spend most of their time at the same length, then having a sudden burst of growth, and plateauing again.
So what does all of this mean?
It means that your child isn’t expected to grow in a consistent, predictable fashion each day or each week. Instead, the “norm” contains periods where growth stalls, followed by a sudden jump, and then another period of static growth. When you have a medically complex child, you often attend more medical appointments where more frequent measurements are taken, so these periods of very normal variation become a lot more obvious! But the most accurate growth assessments often ignore the vast majority of data points, and instead, isolate the growth points that are spaced about 2-3 months apart to get a better overall picture of growth.
It's also important to remember that, if your child was fully tube fed and showing more linear growth, that was likely more a product of the fixed calories day in and day out, calculated specifically to create a certain growth velocity. But with weaning and beyond, parents need to remember oral children don’t consume the same calories each day, and their growth mirrors that variability!
So, if you’re seeing so many data points that make you worry about your child’s growth, remember to allow your child the time to grow as the vast majority of children do, with periods of little to no growth followed by leaps. If you just had a measurement that seems to deviate from their usual, ask yourself if your child is hydrated? Stooling? Happy? Energetic? If the answer to all of these is yes, consider waiting a bit to see if they’re just in the middle of a static period, with a burst of growth likely coming soon.
Hermanssen M, Geiger-Benoit K, Burmeister J, et al. “Periodical changes of short term growth velocity (‘mini growth spurts’) in human growth.” Annals Hum Biol 15, no. 2 (1988): 103-109.
Lampl M, Veldhuis JD, & Johnson ML. “Saltation and Stasis: a Model of Human Growth.” Science 258, no. 5083 (Oct 1992): 801-803.