Plagiocephaly and brachycephaly (flat head syndrome)

6 min read

Many babies develop a flattened head when they are a few months old, usually from sleeping on their back. It often corrects itself over time and is nothing to worry about.

It happens because a baby's skull is still soft enough to be moulded and to change shape if there is constant pressure on one area of their head. The skull is made of plates of bone, which only start to strengthen and fuse together as the child grows older.

Flattening of the head is just a cosmetic problem. It doesn't cause any symptoms and doesn't affect the baby's brain, so their development is unaffected.

The following information explains:

  • the difference between the two types of "flat head syndrome" in babies (plagiocephaly and brachycephaly)
  • why some babies are affected
  • what you can do to help correct it
  • the outlook for your child

Brachycephaly and plagiocephaly

There are two main ways that a baby's head can become flattened:

  • The head can become flattened at one side, causing the head to look asymmetrical and distorted (for example, so that the ears are not aligned). This is known as plagiocephaly.
  • The whole back of the head can become flattened, causing a widening of the head. This is known as brachycephaly. Sometimes, the front of the skull may bulge out in compensation.

Why some babies are affected

The main cause of brachycephaly or plagiocephaly is the baby's sleeping position, although other factors play a part too. These are described below.

Sleeping position

Brachycephaly and plagiocephaly are commonly caused by the baby sleeping on their back every night. The back or one side of the baby's head (if their head naturally rolls to the side) is squashed against a firm mattress for a long time, which eventually forces the soft bone of the skull to flatten.

Once flattened, the baby's head will automatically stay on or roll towards this side. It will become the preferred side for sleeping and for resting their head during the day.

However, the solution is not to change your baby's sleeping position from lying on their back at night. It's important for babies to sleep on their back as this reduces the risk of

sudden infant death syndrome

Instead, change your baby's position during the day to take some pressure of the flattened area (see "What you can do" below).

Factors in the womb

Flattening of the 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 also tends to happen more often in a multiple birth, for example when twins squash against each other in the womb.

Giving birth prematurely

Premature babies are more likely to have a deformed skull because they are squeezed through the birth canal when their skulls have not fully developed (the skull becomes stronger in the last few weeks of pregnancy).

Muscle problems

Sometimes, a baby will have tightened muscles in their neck, which prevents them from turning their head one way. This means they will always rest their head on the other side, causing this side to flatten. Physiotherapy can help correct this problem (see "What you can do" below).


A flattened head may sometimes be caused by the bony plates of a baby's skull joining together abnormally early. This is known as

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

What you can do

No treatment is necessary for mild cases of brachycephaly and plagiocephaly. Your baby's skull should naturally correct itself 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 may find the following advice helpful:

  • 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 there is not constant pressure on one part of their head.
  • Change the position of toys and mobiles in their cot to encourage them to turn their head to the non-flattened side.
  • Consider physiotherapy if your child seems to only be able to turn their head one way. Tight muscles in their neck may be preventing them from turning their head both ways.

It may take six to eight weeks of trying these measures before you notice any improvement in your baby's head shape.

In cases of craniosynostosis, where the plates of your baby's skull have fused too early, surgery will be needed to unlock and move the bones. Read more about the

treatment of craniosynostosis

Should I try a helmet or skull band?

You may have heard about helmets or headbands, known as cranial orthoses, that aim to improve symmetry of a baby's skull. These custom-made devices are designed to be used in infants aged 6 to 12 months (the period of greatest skull growth), to apply pressure to "bulgy" parts of the skull and relieve pressure from other parts, enabling growth in the flatter areas of the skull. The device may also prevent your baby from lying on the flattened part of their head.

However, their use is controversial and they are not available on the NHS. There is currently not enough evidence to say for sure whether a helmet or headband will make any additional improvement to your baby's head shape if the above measures are taken early on.

Also consider that:

  • A cranial orthosis is expensive, costing about £1,700–2,500.
  • The device usually needs to be worn for up to 23 hours a day, for 6–24 weeks.
  • Your baby will need to be reviewed every six weeks to check the device is allowing and not restricting head growth, and for any necessary adjustments to be made.
  • Your baby may find the device uncomfortable, and there's a risk of it causing pressure sores on their head.


Mild flattening of the head usually corrects itself if you use simple measures to take pressure off the affected area of the skull.

More severe cases of brachycephaly or plagiocephaly can still be improved over time, but some flattening usually remains.

A helmet or headband may help correct your baby's skull shape, but this is not certain to work. You should weigh up the inconvenience, expense and possible discomfort to your child before trying this.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.