June 2026
Why Do Babies Get Flat Heads?
You've noticed your baby resting the same way each day, or a subtle flat area starting to form, and now you're wondering: why do babies get flat heads in the first place? The short answer: a baby's skull is soft and still growing, so repeated pressure on one spot can gradually flatten it. It is one of the most common things parents notice in the first months, and it does not mean you've done anything wrong. In this article we explain exactly how babies get flat heads, which factors play a role, and why some babies are affected more than others.
Why babies get flat heads in the first months
A baby's head grows remarkably fast in the first six months. On average, head circumference increases by almost 10 cm, and the head nearly doubles in weight in this short period. At the same time, babies spend the largest part of their day lying down, because their motor skills are not yet developed enough to lift, turn, or reposition the head freely. It is this combination, a fast-growing head plus a lot of time resting in the same position, that explains why babies have flat heads so often in the early months. When steady pressure keeps falling on the same area of the fast-growing skull, that spot expands a little less while the rest keeps growing, and a flat area forms. This does not mean parents are doing anything wrong: back sleeping is still the safest and recommended position for your baby, and a flat spot is simply a common side effect of normal, healthy growth.
What a baby’s head is like in the first months
To understand why early treatment works so well, it helps to know how a baby's head develops. In the first months, the head grows at its fastest: this rapid growth is exactly what makes correction possible. Just as steady pressure can cause an area to flatten while the head is growing quickly, relieving that pressure gives the fast-growing skull room to round back out. The earlier you act, the more of that growth is still ahead of you to work with, which is why a flat spot caught early can often improve with simple position changes alone. To understand what this looks like in practice, read our guide on what does a flat head look like.
What causes a flat head in babies: everyday positions
Most flat heads develop because of repeated pressure on the same area of the head. Looking at the causes of a flat head in infants, this usually happens when babies lie on their backs for sleep, spend long periods resting in the same position, or naturally prefer turning their head to one side. Pressure can also build up when a baby rests frequently in car seats or bouncers, or feeds more comfortably while looking in one direction. A lack of varied movement plays a role too: a flat head from little or no tummy time is common, simply because the back of the head then carries even more of the pressure. Over time, staying in these positions for long periods gradually influences head shape.
When does a flat head start?
Flat spots usually start to appear in the first two to four months of life, and this is also when a flat head tends to happen most. This is the period when babies spend most of their time lying down, have not yet developed strong head control, and cannot reposition themselves. As babies grow, gain neck strength, and begin to roll, sit, and look around more, the pressure spreads more evenly and many flat spots naturally stabilize or improve. This is exactly why the early months are the most important window to keep an eye on head shape.
Why some babies are more affected than others
Several risk factors are known, even though a single clear cause is often missing. Boys develop flat heads more often than girls. One possible explanation: boys have a slightly heavier head on average, so gravity puts more pressure on the skull while they rest. Flattening on the right side is also clearly more common than on the left. Other known risk factors are prematurity, being a firstborn, being one of twins or multiples, and slower motor development, all of which mean a baby tends to move less or rest more in the early weeks. Tight neck muscles deserve a special mention: they are often linked to torticollis in babies, where a preferred head position develops because one side of the neck is tighter, causing the baby to keep resting on the same spot.
Are flat heads genetic?
Parents often ask whether flat heads are genetic, and the reassuring answer is no. A positional flat head is not inherited and does not come from your genes. So is a flat head genetic? In almost all cases, no: it develops from pressure and position, from how a baby lies, how much they move, and how the head is supported in the early months. The known risk factors, such as being born prematurely, being a firstborn or one of twins, or a baby's position in the womb, are about birth circumstances and movement, not heredity. Even the fact that boys develop flat heads slightly more often than girls is thought to come down to a heavier head placing more pressure on the skull, not a "flat head gene". The encouraging part is exactly this: because the cause is positional rather than genetic, it is something you can influence with simple, early changes.
How parents can recognize contributing factors
Recognizing what is contributing to a flat spot helps you act early. Parents may notice their baby often looks to the same side, dislikes turning their head the other way, or spends much of the day in similar resting positions. Spotting these patterns early helps you understand what may be driving the head shape changes, and makes it easier to gently vary positions before a preference becomes a habit. If you'd like a quick structured check, the self-check below takes under a minute.
Why measurement clarifies what is happening
It is genuinely hard to judge a flat spot by eye, even for professionals, because hair, lighting and the natural ridges of a baby's skull all get in the way. A measurement removes the guesswork. A scan can clarify whether flattening is actually present, how pronounced it is, and whether it is changing over time. With the Skully Care app you can do this yourself at home with one photo, which turns vague observations into clear information and helps you take calm, well-informed next steps.
Common questions parents ask
How do babies get flat heads?
From repeated pressure on the same spot while the skull is still soft, usually from lying in the same position. It is a normal side effect of early routines, not a mistake.
Did I cause this?
No. Flat head shapes usually develop from normal early routines such as back sleeping, which is the safest position for your baby.
Are flat heads genetic?
No. Positional flat heads are not inherited. They develop from position and pressure in the early months, not from genes.
When do flat heads usually appear?
Most often between two and four months, when babies spend the most time lying down and cannot yet reposition themselves.
Can this be prevented?
Gentle variation in positions can help, especially early on. For practical tips, read our guide on how to prevent flat head in baby.
Will it always get worse?
In many cases, head shape can stabilize or improve, depending on age, movement, and awareness.
Writen by Elly van der Grift
Elly van der Grift is the co-founder of Skully Care and a pediatric physiotherapist with over 30 years of experience. Her mission is to provide top care for babies with skull deformities. With her infectious enthusiasm, she shares simple, effective tips that can make a big difference for your baby. Working with Elly, you'll feel confident and supported in your baby’s journey to better health.