Plagiocephaly Definition

Plagiocephaly is a condition characterised by an asymmetric head shape deformity, which occurs in early infancy and can continue throughout life. The plagiocephaly definition is summarised by the word plagiocephaly translating as ‘oblique head’. The condition is a deformation of the head, which is marked by an oblique slant to the skull surface. In severe cases, this can also result in facial, cheek, jaw, and ear asymmetry. To learn about the possible longer term effects of plagiocephaly, please read our informative article.

There are many more specific terms to define head shape deformity types, including Positional Plagiocephaly (PP) and Deformational Plagiocephaly (DP). However, these both mean the same thing.

The skull is made up of several ‘plates’ of bone, which are separate in infancy and are connected by flexible ligaments known as sutures. These sutures are there to allow for a normal birth, and to allow the skull to develop as the infant brain grows. They retain some flexibility throughout childhood and as we get older, the bones harden and knit together and create a permanent skull size and shape that cannot change. However, a skull in infancy is soft enough to be moulded into deformation from external pressures. Often, a baby may display birth moulding (in severe cases, known as ‘caput’ head shape asymmetry) immediately after birth, due to pressure from the uterus and birth canal. This usually corrects itself in the first few days of life. After the baby is born, this same flexibility may result in a more lasting re-mould of your baby’s skull if your baby continually lies in the same position for a prolonged period of time.


Since the launch of the “Back to Sleep” campaign in 1994, it has been noticed that more infants are developing plagiocephaly. The back to sleep initiative was developed by the American Association of Pediatrics and has been extremely effective in reducing Sudden Infant Death Syndrome (SIDS). The campaign urged parents to place babies on their back whilst they slept. It has been hugely successful in reducing the incidence of SIDS by over 60%, with many thousands of infants’ lives being saved.

An unintended consequence of the guidelines has seen an increase in positional plagiocephaly as the back of the skull can, in 3% to 5% of infants, begin to flatten when babies sleep exclusively on their back. If you would like to read more information on the relationship between the Back to Sleep Campaign and plagiocephaly, please read our previous post.

Overall, if a baby is not repositioned during the night, or they do not naturally change their sleeping position, the skull shape begins to remodel becoming asymmetric due to an application of continual pressure. We always recommend that parents continue to place their babies on the back to sleep, and to reposition the head so that it does not continue to rest in one continuous position. Our Repositioning Guide details all of the positions that we recommend.

Noticing the indicators of plagiocephaly early on ensures that your baby can benefit from more successful treatment. The key things to look out for are:

• Flattening on either side of the head
• Flattening at the back of the head
• Uneven position of the ears
• The eyes differ in size and position (one eye appears lower/smaller than the other)

You can see more about plagiocephaly on the Channel 4 Embarrassing Bodies Episode Guide, or view the video here.


There is a variety of pillows, cushions and mattresses available on the market. Each of which claim to minimise the development of a flattening. We are not able to give advice on these products and we always refer back to the Lullaby Trust’s advice that, to prevent the risk of suffocation, only the baby should be in the cot and parents should weigh the risk of a flattening against this advice. Once a baby starts to roll onto their side or wriggle and move away from the pillow, which is usually at 3-5 months of age, they become less effective. And if there is a flattening, pillows will no longer be of any significant use. To find out more about creating a safe sleeping environment for babies, please read our related blog post.

If a baby does develop the condition, plagiocephaly treatment options vary depending on the severity of each case. More severe cases of plagiocephaly may warrant the most common treatment, helmet therapy which protects and gently allows the head shape to grow back towards normality. Plagiocephaly helmets are made from a firm outer shell with a soft and comfortable foam lining. The natural growth of the head shape is encouraged by the protective helmet, defending against external pressures. As the skull continues to grow, helmet adjustments are made to accommodate the changing head shape. To put it simply, the helmet provides a protective space for the head to form its natural shape. The average length of treatment can range from 3-6 months, depending on the baby’s age and the severity of each individual case.