Causes of Plagiocephaly

Plagiocephaly (flat head syndrome) can be caused by the position of the baby in the womb and many vaginally delivered babies have asymmetrical heads caused by passing through the birth canal. This usually corrects itself within about six weeks.

It is more common for babies to develop it postnatally usually in the first 4 to 8 weeks due to spending prolonged time in positions which puts pressure on one part of the skull (positional plagiocephaly). Babies skulls are soft and pliable when they are born, this is especially so with premature babies as the bones in the skull harden in the last 10 weeks of pregnancy. External pressure in the first few months can alter the shape of the skull. Babies spend considerable time lying on their back and can develop a flat spot where their head presses against a surface such as a mattress or car seat.

Flat head syndrome is reported to have become more common since the Back to Sleep campaign that began in the early 1990's, since when parents have been advised to place babies on their backs to sleep.  The incidence of Sudden Infant Death Syndrome (SIDS) has halved as a result but experts have noticed a fivefold increase in misshapen heads since then. This, coupled with the time during the day that babies spend sitting and lying in car seats, prams, swings, baby bouncers and activity mats means that a baby’s head is exposed to external pressure for a significant amount of time each day which can leave the back or side of the head with a flattened look. It must be stressed that the benefits of reducing SIDS by continuing to place babies to sleep on their back far outweigh the risk of a baby developing flat head syndrome, which is mainly cosmetic, and parents should continue to place their babies on their back to sleep.

Babies are unable to hold their heads midline, so when sitting in a baby bouncer, car seat or swing the baby will quickly develop a preference for holding her head to one particular side. Often activity mats have little or no padding and they are commonly placed directly on the floor, even a carpeted floor is a hard surface for a baby’s delicate head. All these surfaces, even a mattress or pillow will exert pressure and can affect the baby’s head shape. 

Apparently right sided plagiocephaly is more common than left sided.  The most likely reasons for this is that most mothers are right handed and therefore tend to hold their baby on their left arm (with the right hand side of baby's head resting nicely in the crook of mummy's left arm) and for nappy changes tend to lay their baby down with baby's head at the left side of the changing unit and feet to the right (which means baby will turn her head to the right to look at mummy).  

To avoid baby flat head it is important to vary and alternate the pressure on your baby's head.  When feeding or cuddling your baby alternate the arm on which you hold her.  When holding your baby whilst multi-tasking, again alternate the side on which you hold her and perhaps use a baby sling sometimes.  When putting your baby down for naps, play or nappy changes, place your baby's head at the opposite end each time to alternate the side to which she turns her head.  If you are concerned about baby flat head, please see our practical tips to help avoid and treat baby flat head.