Why Your Baby Has a Flat Head — and What You Can Do About It
Noticing a flat spot on your baby's head can be alarming, particularly when it seems to be developing quickly or when your health visitor mentions it at a check-up. The good news is that positional flat head — known as plagiocephaly — is very common, and when it's caught early, there's a great deal that can be done about it.
Here's everything you need to know: what causes it, when it matters, and what actually helps.
What is plagiocephaly?
Plagiocephaly literally means "oblique head" — it's the term used when a baby's skull develops an asymmetrical or flattened shape. There are a few different patterns:
Positional plagiocephaly — flattening on one side of the back of the head, often with the ear on that side slightly forward compared to the other. This is by far the most common type and is caused by the baby spending time resting on that spot consistently.
Brachycephaly — flattening across the whole back of the head, giving it a wider, rounder appearance. Often seen in babies who strongly prefer lying on their backs.
A combination of both — which is also common.
It's worth knowing that plagiocephaly doesn't affect the brain. The skull is not compressing the brain — it's the external shape that's changing, not the space inside. That said, it's worth addressing, both because the window for natural correction is relatively short, and because the underlying cause (a head position preference or neck stiffness) is worth treating in its own right.
What causes it?
A baby's skull at birth is made up of soft, flexible bony plates — this is what allows the head to pass through the birth canal, and it's what makes normal brain growth possible in the first year of life. That same flexibility means the skull is susceptible to reshaping under sustained pressure.
The most common causes of positional plagiocephaly include:
A consistent head position preference — if a baby always turns their head to the same side when lying down, one part of the skull takes repeated pressure while the other side is relatively unloaded. Over time, this creates asymmetry.
Neck stiffness or torticollis — often the underlying reason a baby has a head position preference in the first place. If the muscles on one side of the neck are tighter than the other — frequently as a result of positioning in the womb or of the birth itself — the baby finds it more comfortable to rest with their head turned one way. Treating the neck stiffness is often the most important part of addressing the flat head.
Time spent in car seats, bouncers, and swings — all of these involve the back of the head resting on a firm surface, adding to the total pressure load. This doesn't mean avoiding them, but being mindful of the balance between time in these positions and time on the tummy or being held upright.
Premature birth — premature babies have softer skulls and often spend extended time lying down in hospital care, which increases their risk of developing plagiocephaly.
When should you act?
The earlier the better. A baby's skull is most malleable in the first few months of life — this is both why plagiocephaly develops relatively quickly and why it responds well to treatment and repositioning during this window. The rate of natural correction slows significantly after around five to six months as the skull becomes less flexible, and by twelve months the bones are considerably more fixed.
This doesn't mean nothing can be done after six months — but it does mean that if you've noticed a flat spot and your baby is under four months, acting now rather than waiting to see if it improves on its own is worthwhile.
What can you do at home?
Tummy time — the single most effective repositioning strategy. Time spent on the tummy takes all pressure off the back of the skull and builds the neck and shoulder strength babies need for sitting, crawling, and rolling. Aim for short, regular sessions throughout the day from birth — little and often works better than one long stretch. Always supervised, and never for sleep.
Varied positions when awake — alternate which end of the pram or cot your baby's head is at, change arms when carrying, and try to minimise time in car seats and bouncers when not travelling.
Repositioning during sleep — you can gently encourage your baby to turn their head to the less-preferred side when you place them down to sleep, or alternate which side of the cot you approach from so they naturally turn the other way to look at you. Safe sleep guidelines (baby on their back) should always be followed.
Plagiocephaly pillows — memory foam pillows with a central cut-out that reduces pressure on the back of the skull are widely available and can be useful, particularly for babies who strongly resist repositioning. These sit under the sheet, not loose in the cot.
How can osteopathy help?
Repositioning advice addresses the symptom — the sustained pressure on one part of the skull. But if there's underlying neck stiffness or muscle tightness driving the head position preference, repositioning alone will only go so far.
This is where osteopathy makes a significant difference. By assessing and treating the muscular and joint restrictions in the neck, jaw, and base of the skull — often stemming from the birth itself — osteopathic treatment helps the baby move their head more freely and comfortably in both directions. When the preference resolves, the pressure on the flat side reduces naturally, and the skull begins to reshape.
Research by Lessard et al (2011) supported the use of cranial osteopathy in improving cranial asymmetries, with more significant results in babies under six months — reinforcing why early treatment matters. Amiel-Tison and Soyez-Papiernik (2008) also showed that cranial osteopathic treatment significantly decreased the degree of asymmetry in babies with plagiocephaly.
Alongside hands-on treatment, I'll give you specific positioning and tummy time advice tailored to your baby and their particular pattern of flatness.
What about helmets?
Cranial remoulding helmets — custom-made orthotics worn for most of the day — are sometimes recommended for babies with more significant plagiocephaly that hasn't responded to repositioning and conservative treatment. They're generally most effective between four and twelve months, and work by creating a void on the flat side of the helmet so the skull can grow into it.
Helmets aren't always necessary, and they aren't always the right next step — but for moderate to severe cases that haven't responded to earlier intervention, they're a legitimate and effective option worth discussing with a specialist. If we reach that point, I can refer you to the appropriate service.
When to see a GP
Most plagiocephaly is positional and responds well to the measures above. However, it's worth speaking to your GP if:
The flatness is severe or involves the front of the skull as well as the back
There are ridges or raised areas along the skull sutures (the joins between the bony plates)
You have any concern it may be craniosynostosis — a rare condition where the skull sutures fuse too early
In the vast majority of cases, this won't be the explanation — but it's always right to rule it out if you have any concern.
If you've noticed a flat spot on your baby's head and would like an assessment, I'd encourage you to get in touch sooner rather than later. You can read more about osteopathy for babies and children and cranial osteopathy, or book an appointment directly. I'm always happy to have a quick chat on the phone first if you'd like to talk things through before booking.
— Sally