Tummy time, the recommended practice of putting a baby prone on the floor (whether they like it or not), feels deeply connected to the experience of raising a baby in America. But look into baby books published prior to the 1990s and there’s no mention of the practice.
There’s a good reason for that. Before 1994, tummy time did not exist.
READ MORE: The Fatherly Guide to SIDS
Until the American Academy of Pediatrics (AAP) started recommending that babies sleep on their backs to prevent Sudden Infant Death Syndrome, nobody spoke about tummy time. The recommendation for back-sleeping saved countless lives, but at a developmental cost — infants who would have learned to crawl in their cribs were put on their backs at a time when rolling over, pushing up, and crawling muscles were ripe to develop. The story of how tummy time emerged as the best way to get kids crawling safely is one of unintended consequences, and a modern example of how society and science can shape childhood development in real time.
A look into why tummy time is recommended in the first place offers clues as to how it came to be. Pediatricians say placing children on their bellies is meant to get them to push up on their arms, stretch their necks, and look around. This helps develop the muscles needed to progress toward milestones known as “prone skills”, which include rolling over, pushing up, and crawling.
“The more waking hours babies spend on their tummy, the earlier on average they will roll over, push up in a prone position, called prone prop, and crawl,” Dr. Karen Adolph, director of the NYU Infant Action Laboratory told Fatherly. Babies, it turns out, aren’t big fans of being face down. “Babies don’t really like being on their tummy because it takes more work to fight gravity.”
But if tummy time is a relatively new phenomenon, how did kids manage to build strong muscles prior to the now-mandatory prone workouts? They did it in their cribs, of course.
In 1994, AAP began telling parents that babies should be placed on their backs to sleep. The so-called Back-to-Sleep initiative launched in response to data that suggested that children who sleep on their tummies are more susceptible to SIDS. The campaign—led by pediatricians and supported by pamphlets, ads, and posters—was a smashing success. In response, many parents began putting their babies to sleep in supine positions. And SIDS deaths did decline.
A few years later, however, pediatricians began to notice that back-sleeping was slowing down movement milestone acquisition, particularly for the prone skills. In 1998, a longitudinal study of 350 babies showed that, indeed, back sleepers were arriving at the rolling over and crawling milestones later in life.
“Babies who went to sleep on the tummy might wake up in the middle of the night. Or they might wake up before they start fussing and the parent comes to get them,” says Adolph. “All that time they’re pushing up in prone and lifting their head out of the mattress.”
But letting babies sleep prone wasn’t an option, so tummy time was born and AAP released a revised campaign—Back-to-Sleep, Front-to-Play. Pediatricians now recommend that tummy time begin as soon as possible, starting with 2-5 minutes of supervised, front-down play.
Despite this initiative, however, prone skills are still slightly delayed in kids who sleep on their backs and rely on tummy time — perhaps due to iffy compliance. “A lot of babies cry because it’s a lot more trouble than lying on their back and having their parents bring everything to them,” Adolph says. “So the parents are loath to keep them on their tummy because they’re fussy.”
Not that meeting milestones really matters in the grand scheme of things. Adolph notes that the acquisition of movement milestones varies greatly based on differences in childrearing practices linked to historical, cultural, and ethnic groups. The window for achieving these milestones can span months and, of course, even if parents spurn tummy time and fail to encourage their children to reach milestones, kids figure out how to crawl eventually. Far more interesting, Adolph says, is that the tummy time phenomenon is just one example of how differences in parenting practices can influence child development. At the turn of the 19th century, babies were also slower to crawl — because back then, most kids spent their earliest months in bulky christening gowns. “Log rolling” in this population, however, was common.
Adolph suspects that tummy time won’t be the last parenting trope to affect how children develop in the United States, and beyond. “You don’t have to go to Mali or Cameroon or some exotic location to see how child-rearing practices affect children’s motor skills,” she says.
“It happens in our own culture. It’s happened in my lifetime.”