Why Do Babies Get Flat Heads? A New Perspective

I vividly remember this question two months after I gave birth to my eldest. I noticed that the back portion of his head is flat, so I asked my mom, “Why do babies get flat heads?”

Being the sarcastic mom that she is (but I love her to bits!), she replied, “That’s because you let him sleep on his back all the time.”

Then I asked, “Will a baby’s flat head correct by itself?”

She said no.

Of course, I believed her. At least at that time. I thought my son’s skull is forever doomed.

I had completely forgotten about it when I noticed his head is almost back to normal. I guess he was about three at that time.

So my mom lied?


Not really. My mom is a traditional mother who believes in what her parents told her. Perhaps it’s what she learned from her parents as well, which she tried to pass on to me.

However, my mom’s belief may be partly correct. I’ll talk more about this later in this article.

Let’s answer first what really happened to my son’s head and how it got its shape back.

Why Do Babies Get Flat Heads?

sleeping baby

Deformational plagiocephaly (DP) and brachycephaly are the medical terms for flattened heads. The former is when the flatness is on one side only, making the head look asymmetrical. The latter is flatness of the back of the head. In general, however, DP may refer to both.

Now, back to the question.

Babies get flat heads because they have soft skulls. (And thank God that’s the case. Otherwise, I can’t imagine how I’d be able to have a normal vaginal delivery.)

According to Nationwide Children’s Hospital, it takes about 9-18 months before the skull is fully formed. During those formative months, the skull is soft. Thus, it can be deformed as our babies don't move a lot when they're lying down. They're mostly in the supine position the first few months of their lives.

This repetitive supine position causes asymmetry.

But I came across an interesting perspective as I was researching. This is where I’ll explain why my mom could not be totally wrong.

In 2018, researchers Renz-Polster and De Bock hypothesized that a parent's beliefs might have something to do with DP. The researchers questioned,

"if the supine sleeping position is the safest position for infant sleep—why should it result in a social handicap for a significant proportion of babies?"

Clearly, there should be a better explanation than this.

The researchers also presumed that it could be the industrialized countries’ practices that are causing DP. More specifically, the researchers pointed out bottle feeding, traveling in fixed physical structures, and not bed-sharing could be the culprits.

I’ll try to explain why in the following sections:

1. Breastfeeding

Breastfeeding has probably been the only feeding method during the hunting-gathering era. Its position is also repetitive, but "[it] has certainly not been associated with prolonged gravitational pressure to a specific portion of the skull," says Renz-Polster and De Bock.

On the contrary, bottle-feeding is (associated with prolonged gravitational pressure). Hence, it causes DP.

2. Transport

We usually transport our babies now in car seats, strollers, or prams. Back then, the primary mode of transportation for the little ones is being carried by their caregivers using either slings or bare arms.

The latter is assumed not to have as much gravitational impact on the skull as the modern methods do, which is why it probably didn’t cause DP. If it did, it could have been minimal.

3. Infant sleep

The American Academy of Pediatrics discourages bed-sharing because it increases the risk of SIDS. Not all parents are light sleepers; hence, it’s better not to co-sleep.

However, Renz-Polster and De Bock assert that when babies sleep alone, their heads are hardly repositioned. Bed-shared babies, in contrast, are almost always checked on, repositioned, nursed, and so on. These movements mean there's less prolonged pressure on one side of the head. Thus, lessening the risk of DP.

4. The Research Conclusion

The research concluded that there could be an inverse correlation between traditional childcare and DP. However, the authors admit one thing.

These are mere hypotheses. Future research should carefully study this in the future. The researchers suggested comparing industrialized societies with different parenting styles.


baby sleep with mom

Another study may just be supporting the two researchers mentioned above, even before their research was published. According to Aarnivala et al., the traditional way if child-rearing can indeed prevent DP.

In 2015, these researchers invited 111 pregnant mothers to participate in the study. They were divided into two groups: control and intervention.

When their babies turned three months, the researchers found out that the prevalence of DP in the intervention group was 11% while it was 33% in the control group.

What made the difference?

The intervention group was given the following instructions on how to correct baby flat head (or at least avoid them):

  • Alternate the position of the head. Whether your baby is sleeping or being carried in a stroller, car seat, or carrier, you should alternate her head position between left and right from time to time. If she sleeps on one side, switch regularly. Also, provide enough room for movements.
  • Alternate head position during feeding. Whether breast or bottle feeding, you should also alternate sides.
  • Give tummy time. When your baby’s awake, give her supervised tummy time for a few minutes. I would do this to my son every day then turn him over when he’s about to cry from that position.
  • Make room for play. Your little one should have enough space during playtime, advises Aarnivala and colleagues. Avoid hanging toys. Instead, spread them on the floor or her bed. Also, try to get her attention from both sides to cranial asymmetry.


Based on this information, my mom’s answers to the question “Why do babies get flat heads?” and “Will baby flat head correct by itself?” seem plausible.

Babies get flat heads because their skulls are soft. They will remain flat if you don’t do the preventive steps on how to correct baby flat head outlined above.

Sarah Morgan

Chief editor of WellBeingKid.com and striving mom-extraordinaire.Let me share and inspire you with my daily struggles to live a healthier and more fulfilling life.

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