Developmental milestones are a valuable medical tool, but is our obsession with them causing unintended consequences?
As you scroll through parenting feeds on social media, you’ll notice so-called milestone cards: pastel-colored cards that mark a baby’s first attempt at crawling, sitting up, or walking, along with their age. Developmental milestones have become something to celebrate – or stress about – not just on social media. According to one recent poll, roughly six in ten US parents are concerned about their babies meeting developmental milestones. But no one knew when or what would happen.
Others may take the opposite approach, paying little attention to the timing of new skills and trusting that their child will develop at their own pace.
This begs the question: what are milestones for, and how should parents use them? Are they a valuable tool that can alert us when something is off track? Or are they just another way for parents to “out-parent” one another?
The answers are partly dependent on what we mean by milestones. For starters, the reasons given by healthcare professionals for their importance may differ from those given by parents.
“A milestone is a description of a child’s behaviour that parents either say their child can or cannot do,” says Chris Sheldrick, a research associate professor at Boston University who specialises in paediatric screening protocols.
He emphasises the literal meaning of the word. In a 10K race, there may be a marker: a milestone, at the 5K mark. No one has passed it at the start of the race, by definition. Everyone has by the end of the race.
Checking a baby’s progress along those markers can assist healthcare professionals in assessing their development. Experts say that because parents know their child best, it can be a good idea for them to know roughly when babies tend to do things for the first time (though there are important caveats to the idea of typical development, which we’ll get to later).
When parents have a laid-back attitude toward developmental milestones – If parents assume that their child hasn’t tried crawling or walking because they have a more laid-back personality, for example, they may be overlooking other explanations, according to healthcare professionals.
“There are children whose personalities influence what they are willing to do. So they could be the ones who are heading in that direction “says Kaitlin Rickerd, a New York-based paediatric physical therapist. “However, when it begins to fall outside of the expected ranges, there is usually something that needs to be addressed. There is a reason, no matter how big or small.”
Developmental delays are common, affecting one in every six children in the United States. A delay alone does not indicate a medical condition; for example, in one study of 404 18-month-olds who were not walking independently, two-thirds had no underlying pathology.
When there is a problem, however, intervening as early as possible is critical. Delayed speech, for example, can indicate autism, whereas late walking can indicate cerebral palsy. Early detection of such differences can assist parents in understanding and supporting their child’s unique development.
“We know that in the first three years of life, the amount of brain growth, learning, and milestones that a child acquires is enormous -“It’s also our best opportunity to get in there and make a difference,” Rickerd says.
There is some evidence that hitting certain milestones early can be indicative of future educational attainment
However, she claims that milestones are more than just a tool for identifying underlying issues. She realised a failure to master one skill could have resulted in a cascade effect while working in paediatrics with older children. She explains that struggling to hold a pencil to write may be related to weakness in the arches of a child’s hands, which may have been influenced by not being weight-bearing as a baby, whether through crawling or tummy time.
This professional perspective on milestones as primarily a screening tool differs from how some parents regard milestones in everyday life: as a predictive, and sometimes competitive, indicator of ability or talent.
Indeed, there is some evidence that achieving certain milestones early can be indicative of higher intelligence or later attainment of more education. However, according to Sheldrick, this is true for entire populations rather than specific children. If a typical developing child has a one-in-a-million chance of becoming a professional soccer player, an early walker may have a one-in-900,000 chance, he says.
Furthermore, pressuring children to meet milestones can backfire. There is some evidence that frequent use of baby walkers and jumpers, for example, can impede motor development.
According to Sheldrick, the metaphor of a race with each mile marked by a stone does not quite fit the complex reality of human development. When you’re watching a race, you can tell which runners are exactly 1K behind the 5K mark. You can guess when they’ll hit it. When they do, you’ll know exactly when it happened. And every runner who completes the race will arrive at some point.
This clarity is not provided by developmental milestones. They are also not a universal concept. Their interpretation and definition can vary greatly across cultures – and even within individual families.
“A good example is, ‘Can your child walk?'” says Sheldrick. “What exactly do you mean by ‘walk’? Is your child able to walk a mile? Can they walk all the way to and from the well? “Have they made any progress?”
Because of this ambiguity, new screening tools, such as the updated milestones recently released by the US Centers for Disease Control and Prevention (CDC) and American Academy of Pediatrics (AAP), attempt to use more specific language.
How do you decide when something ‘should’ happen? And what data is that based on?
Making matters more difficult is the fact that children grow at a rapid pace. A child who isn’t walking at 18 months may be running by 19 months. But if the child is only tested at 18 months, they might be identified as not being “on track”.
Then there’s the measurement problem. How do you determine when something “should” occur? And on what data is this based?
Many of these issues were highlighted by a recent change to the CDC and AAP’s milestones list. For nearly 20 years, they based milestones on the 50th percentile, as do many other official milestone lists – if 50% of children could do something by a certain age, that was the age for that milestone.
This meant that the other half of carers might be overly concerned. It also encouraged paediatricians to take a “wait and see” approach with children who had not reached a developmental milestone, which occasionally backfired. “Parents of disabled children reported identification delays because they were told to wait, that children develop differently, and that some take longer than others,” researchers involved in the changes wrote.
As a result, the CDC increased its benchmarking to the 75th percentile in early 2022. However, the risk now runs the other way: as the ages are set later, families may notice a child’s delay later as well.
Then there’s the issue of where these expectations originate.