When I took my son Edwin to the pediatrician for his 3-month check up, everything looked completely normal. He was gaining weight (85th percentile in fact) and he was meeting all of his milestones. All seemed well; that is, all except for one thing. The doctor said that he was showing signs of a condition called plagiocephaly, which literally means flat head. She advised seeing a physical therapist, and as an obedient new parent I followed her orders and made an appointment for the following week. The physical therapist confirmed that he had a flat head from sleeping on his back, and warned us that not taking action to treat it and failure to encourage Edwin to spend more time on his belly could lead to a more permanent flat head and delayed motor milestones like crawling. She recommended weekly (and very expensive) physical therapy sessions for at least 6-8 weeks.

When you throw big technical-sounding words around like plagiocephaly and warn about anything being “delayed”, a new parent is likely to pay whatever they can afford for those extra doctors’ visits to fix whatever the problem might be. Sometimes immediate action is warranted, but you have to wonder whether sometimes parents’ fears are being taken advantage of, and whether expensive physical therapy sessions are necessary to “fix” a newborn’s flat head.

Plagiocephaly is a relatively new diagnosis and first became popular after the 1990’s when the National Institutes of Health launched the “Back to Sleep” movement. Before this movement, the common wisdom was to place infants to sleep on their stomachs so that they wouldn’t choke or suffocate if they were to spit up at night. Research suggested that in fact infants who slept on their backs pretty much never choked to death on their own spit up, and more importantly, were at a markedly lower risk for dying of SIDS. SIDS—or Sudden Infant Death Syndrome—is the unexplained death of an infant while sleeping. Although no one knows exactly what causes SIDS, researchers believe that infants who sleep on their stomachs might have trouble rousing themselves if they need more oxygen, whereas infants that sleep on their backs can simply turn their heads to get more air. Consistent with this theory, proponents of the Back to Sleep movement (and any doctor or nurse you talk to today) urge parents to put their infants to sleep on their backs instead of on their stomachs. Their recommendations turned out to be really good ones, and there has been a dramatic drop in the rate of SIDS in the United States ever since.

 Oleg Sidorenko/flickr
Source: Oleg Sidorenko/flickr

Although putting babies to sleep on their backs has had a remarkable and important impact on SIDS deaths, there have also been some unintended consequences. First, babies began developing flatter heads from spending so much time on their backs, and hence plagiocephaly became a popular diagnosis. Second, babies started experiencing delayed motor milestones, such as later crawling and walking. Since spending more time on your back means spending less time on your stomach, babies are now getting fewer opportunities to practice pushing themselves up and developing the strength they need to move around on their own.

Again, the idea of anything being “delayed” might sound scary to a new parent. But what are motor milestones, and why are they so important? You can see posters illustrating the motor milestones in any pediatrician’s office. They even appear on a card I received from Mount Sinai Hospital when Edwin was born that I can use to track his development. Motor milestones are averages for when you can expect your infant to be sitting (~6-7 months), crawling (~8-9 months), and walking (~12-13 months) to name a few. These milestones were originally inspired by research from the early 1900’s and has clearly lasted the test of time. But, using the term “milestones” can be misleading, as it implies that these motor developments have to happen during a predetermined and very precise window of time.

It turns out that motor “milestones” are quite malleable based on specific cultural and generational differences. For example, babies born after 1990 crawl and walk later than babies born before the Back to Sleep movement. Babies who are carried or swaddled all day are also likely to crawl or walk later than babies who are free to move around. Babies who are given extra opportunities to develop their motor abilities (for example, by being put in a walker) might crawl or walk sooner than other babies. Some infants skip crawling altogether, while others find alternative ways of crawling (like “army crawling” or “bum shuffling”) that don’t involve being on your hands and knees. In fact, milestones can be affected by something as simple as weight, with heavier babies developing certain abilities later than thinner ones based on the fact that heavy legs require more muscle to lift than light ones do.

Is there something wrong with weird crawlers, late crawlers, or non-crawlers? Absolutely not. There is no evidence that not crawling or late crawling has any negative downstream effects on development whatsoever. All typically developing infants will eventually learn how to walk. Extreme motor delays such as no signs of walking by 18-24 months can signal more serious developmental or neurological disabilities (e.g., Down syndrome, cerebral palsy) and warrant seeking a specialist. But if you’re concerned about avoiding motor delays in an otherwise healthy infant, or want to reduce the flat head issue, there are a few things you can do.

The most extreme and expensive route is to seek physical therapy to treat these issues directly. It might cost you, but I’m of the camp that thinks you should do whatever you need to do to reduce stress as a new parent, so if you’re worried, go for it—a consultation couldn’t hurt. But be cautioned: Although there is research showing that therapies (e.g., wearing a helmet) for plagiocephaly are effective, there are other studies suggesting that these therapies are no more effective than just letting the issue work itself out on its own. So the other extreme is to simply wait for these issues to fix themselves, and they oftentimes do.

Finally, you can also take a middle of the road approach and keep your baby off his or her back while awake, and try doing “tummy time”—or putting him on his stomach to play—for 15 minutes at a time several times a day. This is probably what your doctor or a physical therapist would tell you to do anyway. Daily tummy time keeps babies off their flat heads during the day, and helps them practice holding up their heads and pushing up their torsos, giving babies the upper body strength they need to start moving around on their own. As soon as they can turn themselves over, they probably won’t want to spend much time on their backs anymore. Soon after, you’ll have a whole new problem on your hands—a crawling baby.

We decided to take the “wait and see” approach and Edwin crawled right on time (despite the fact that he’s 85th percentile in weight) and his head has rounded out nicely. You might call me a bad mother for saying this out loud, but being a new parent is tiring enough as it is without having to chase a very fast 1-year-old around the house, so a little bit of a delay in Edwin’s crawling doesn’t sound like it would have been such a horrible thing in the end.