Babies sometimes develop a flattened head when they’re a few months old, usually from sleeping on their back.

It’s known as “flat head syndrome” or “moulding” and there are two types – plagiocephaly and brachycephaly (see below).

If a baby has a flattened head, it isn’t usually a cause for concern because it will often correct itself over time.

Plagiocephaly and brachycephaly

The two types of flat head syndrome in babies are: 

• Plagiocephaly – this is the most common type and occurs when the head is flattened on one side, causing it to look asymmetrical and distorted. For example, the ears may be misaligned and when seen from above the head, looks like a parallelogram.
• Brachycephaly – this is when the back of the head becomes flattened, causing the head to widen. To compensate, the front of the skull sometimes bulges out.

What causes plagiocephaly and brachycephaly?

The skull consists of plates of bone, which start to strengthen and fuse together as a child develops and gets older.

A young baby’s skull is still soft enough to be moulded and change shape if there’s constant pressure on a particular area of their head.

The following information explains:

• Why some babies are affected.
• What you can do to help correct it.
• The outlook for your child.

Why some babies are affected

A baby’s sleeping position is the main cause of plagiocephaly and brachycephaly, although there may be other factors at work.

Sleeping position

Plagiocephaly and brachycephaly are often caused by a baby sleeping on their back every night.

Should the back or one side of the baby’s head (if their head naturally rolls to the side) be squashed against a firm mattress, the soft bone of their skull can become flattened.

Once their head is flattened, it will automatically stay on the flattened side or roll towards it. This will then become their preferred side for sleeping and for resting their head during the day.  

However, don’t change your baby’s sleeping position from lying on their back at night. It’s very important for babies to sleep on their back, because it reduces the risk of sudden infant death syndrome (SIDS).

Instead, you should change your baby’s position during the day, to relieve some pressure from the flattened area (see below).

You can buy specialist curved mattresses that are designed to distribute the weight of a baby’s head over a larger area, so that less pressure is placed on any point of their skull. However, there’s a lack of scientific evidence demonstrating that these mattresses are effective in treating or preventing plagiocephaly.

Factors in the womb

Flattening of a baby’s skull can sometimes occur in the mother’s womb.

There may not be enough amniotic fluid inside the womb to cushion the baby (known as oligohydramnios). This means the baby’s head can become temporarily deformed as they travel down the birth canal.

This tends to happen more often in multiple births – for example, when twins squash against each other inside the womb.

Premature births

Premature babies are more likely to have a deformed skull because they’re squeezed through the birth canal when their skulls haven’t fully developed (the skull strengthens during the last few weeks of pregnancy).

Babies born prematurely tend to be nursed with their head on the side (alternately), which means they can develop a longer, thin head. As these babies are born early, they also have a longer period of time before they develop head control and are able to spontaneously move their head.

Muscle problems

A baby will sometimes have tight muscles in their neck, which prevents them from turning their head a particular way.

This causes them to always rest their head on the other side, flattening it. Physiotherapy can be used to help correct this problem (see below).

Craniosynostosis

A flattened head can sometimes be caused by the bony plates of a baby’s skull joining together too early. This is known as craniosynostosis.

This can pull the baby’s head out of shape and may need to be corrected with surgery (see below).

What you can do

Treatment may not be necessary in mild cases of plagiocephaly or brachycephaly.

Your baby’s skull should correct itself naturally over time if you take some simple measures to take pressure off the flattened part of their head and encourage them to try different positions.

You should:

• Give your baby time on their tummy during the day and encourage them to try new positions during play time.  
• Switch your baby between a sloping chair, a sling and a flat surface, so that there isn’t constant pressure on one part of their head.
• Change the position of toys and mobiles in their cot to encourage your baby to turn their head to the non-flattened side.
• Consider physiotherapy if your child is only able to turn their head one way; tight neck muscles may be preventing them from turning their head to the other side.  

You may need to try these measures for six to eight weeks before you notice an improvement in the shape of your baby’s head.

In cases of craniosynostosis, where the plates of your baby’s skull have fused too early, surgery may be needed to move the bones.

Read more about how craniosynostosis is treated.

Headband or helmet therapy

Helmets or headbands, known as cranial orthoses, improve the symmetry of a baby’s skull.

These custom-made devices apply pressure to “bulging” parts of the skull and relieve pressure from other parts, allowing growth in the flatter areas. The device may also prevent your child lying on the flattened part of their head.

Cranial orthoses are designed to be used while a baby’s skull is still soft and malleable. Treatment should be started when the child is around five or six months old. To be effective, the device should be worn continuously (up to 23 hours a day).

Helmet therapy usually takes three to six months to complete and is often used until the child is about 14 months old. However, it can sometimes take longer for treatment to be successful.

The use of helmets and headbands is controversial, and they’re not available on the NHS. This is because there’s not enough evidence to show whether a helmet or headband will make any improvement to the shape of your baby’s head if the above measures are taken early on.

Other things to consider:

• Cranial orthoses – these are expensive, costing around £1,700-2,500.
• Your baby will need to be checked every six weeks to make sure that the device is allowing (and not restricting) head growth, and for any necessary adjustments.
• The device may be uncomfortable, and there’s a risk it will cause pressure sores on your baby’s head.

Outlook

Mild flattening of the head will usually correct itself if you use the simple measures outlined above, which are designed to relieve pressure from the affected area of your baby’s head.

More severe cases of plagiocephaly and brachycephaly can still be improved over time, although some flattening will usually remain.

As your child’s hair grows and they develop good head control, the cosmetic aspect should improve. It’s very rare for a child to be referred back to a specialist when they reach school age because of teasing.

A helmet or headband can be used to help correct the shape of your baby’s skull, but it may not work in all cases. You should consider the inconvenience, expense and possible discomfort to your child before trying a headband or helmet.

Also, the lack of scientific evidence that these devices do more than the measures outlined above makes it difficult for the NHS to support their use.