Searching for the Cause of Plagiocephaly

Skulls are not perfectly smooth structures - there can be lumps, bumps and flat areas. Occasionally babies can develop a persistent flat spot on the back or side of the head. It is usually easy to treat and following appropriate intervention will correct itself.

It has long been thought that factors before and are birth contribute to the development of positional plagiocephaly and these include:

Sleep position - babies spend many hours lying on their backs asleep, and this is assumed to contribute to the flat shape

Overcrowding in the womb - a problem amongst twins and other multiple births

Premature births - the skulls of premature babies are softer than full-term babies. They also spend a lot of time on their backs without being moved because of their condition

But what increases a baby's risk of developing plagiocephaly flat head? Is it genes, the environment or both?

To find the answer to this Dr. Brian C. Verrelli and his research colleagues carried out a huge study of more than 20,000 babies with deformational plagiocephaly, and they published their results in the journal Pediatrics.

Previous studies had suggested that there could be a genetic predisposition to developing the condition because it has been observed to run in families. However, many feel that such research is inconclusive as it could either reflect genetic influences or parental practices.

In Verrelli's study researchers discovered that there was a higher risk of developing plagiocephaly amongst twins, but this did not suggest a genetic risk or predisposition because there was no difference observed between identical and fraternal twins.

Identical twins share all of their genes and fraternal twins share half of theirs. If there is a genetic cause for a trait under investigation you would expect to see a higher frequency of the genetic variants in the identical twins. It is why identical and fraternal twins are used in genetics research - to help tease out the roles of nature and nurture - genes and environment.

Sleep position - this was found to be the most important factor. Babies who slept mostly to the right developed a flat spot on the right side of their head, and those that developed a flat spot on the left side of their head had slept predominantly to the left.

Position in the womb is important - 15% of plagiocephaly babies in this study were born in the breech position, with the buttocks or leg near the birth canal instead of the head. This percentage compares to about 4% breech births in the general population.

The scientists are not ruling out a genetic predisposition; there may be several at play amongst different populations. But at the moment the research shows that environment is of paramount importance, which suggests that it can be avoided and easily treated.

Since paediatricians recommended putting babies on their back to prevent sudden infant death syndrome (SIDS) there has been an increase in the number of babies with plagiocephaly. The advice they offer now is not to change this, but when the babies are awake ensure that they get plenty of "tummy time" and to avoid leaving them in swings or seats for long periods. As always the recommendation is to seek the advice of the professionals if in any doubt.