Plagiocephaly (Flat Head)

What is plagiocephaly?

Plagiocephaly is a flattening of one part of a baby's skull — most commonly the back or one side of the head. It happens because a baby's skull is soft and pliable in the first months of life, and consistent pressure on one area can change its shape.

It became more common after public health guidance recommended that babies sleep on their backs to reduce the risk of cot death. That guidance is right and shouldn't be changed — but one consequence is more babies developing flat areas on the back of the head.

It's important to understand what plagiocephaly is not. In the vast majority of cases, it does not affect brain development, it is not painful or harmful to the baby, and it is not caused by anything a parent has done wrong. It's primarily a cosmetic issue, and one that usually improves significantly as the baby grows.

What does it feel like?

Babies don't show symptoms in the way older children do — plagiocephaly is something parents notice rather than something the baby complains about. Common observations include:

• A flat area on the back or side of the head

• One side of the head appearing more rounded than the other

• An ear that looks pushed forward on one side

• Asymmetry in the forehead or face when viewed from above

Some babies also have a tight neck muscle on one side (torticollis) which makes them prefer turning their head one way — this can both contribute to and result from plagiocephaly.

How is it diagnosed?

Diagnosis is usually straightforward and based on examination — looking at the shape of the head from above and from the sides, and assessing the neck and overall development.

The most important thing the assessment does is rule out a much rarer condition called craniosynostosis, where the bones of the skull have fused too early. This is a different problem requiring different management, and it's vital that the two are distinguished.

Imaging isn't usually needed for typical plagiocephaly — but it may be arranged if there's any uncertainty about the diagnosis.

What are the treatment options?

Most cases of plagiocephaly improve with simple measures: repositioning during sleep and play, plenty of supervised tummy time, and addressing any neck tightness. Babies' skulls have remarkable capacity to remodel as they grow, particularly in the first six months.

Helmet therapy is sometimes considered for more severe or persistent cases, typically started between 4 and 6 months of age. It isn't right for every baby, and the evidence around it is more nuanced than it's sometimes presented. Nev will help you understand whether a helmet is likely to add meaningful benefit in your child's specific situation.

When should you get it checked?

Seek a specialist assessment if:

• The flat area isn't improving with repositioning by 4 months of age

• The asymmetry seems significant or is getting worse

• Your baby strongly prefers turning their head to one side

• You're worried about the shape of your baby's head and want a clear answer

• You're being offered a helmet and want a second opinion before committing

Plagiocephaly is one of those areas where a calm, experienced assessment makes a real difference — both in identifying the small minority of cases that need active treatment, and in reassuring families when reassurance is what's needed.