New research published in the BMJ suggests that for positional skull deformation in infants - flattening of the skull as a result of laying in the same position for long periods - wearing a corrective helmet does not improve the condition.
It is unknown as to how many infants in the US experience positional skull deformation, also known as flat head syndrome. In the UK, it is estimated to affect 1 in 5 babies under the age of 6 months.
There are two types of positional skull deformation - plagiocephaly and brachycephaly. Plagiocephaly occurs when one side of the head becomes flat, causing the infant's ears to become misaligned. Brachycephaly is when flattening occurs on the back of the head, causing the front of an infant's skull to bulge.
Since the skulls of young infants are very soft, constant pressure on a specific area of their head can cause it to change shape. This is what happens in positional skull deformation. It is mainly caused by a baby's sleeping position.
Past studies have shown that since the launch of the American Academy of Pediatric's (AAP) "Back to Sleep" campaign in 1992 - which recommends that parents should position babies on their backs when sleeping to reduce the risk of sudden infant death syndrome (SIDS) - there has been a dramatic increase in the number of children affected by positional skull deformation.
In most cases, a baby's skull will correct itself over time. But in more severe cases, treatment may be required. This may involve the use of helmets, known as cranial orthoses.
The idea is that the helmets stop the infant lying on the flattened area of their head. Treatment is usually started when the infant is 5 or 6 months old - when their skull is still soft enough to be moulded. The helmet is required to be worn up to 23 hours a day, and full treatment usually takes around 3-6 months.
But in this latest study, researchers from the Netherlands have questioned the benefits of such treatment.
According to the team, there has been little research comparing helmet therapy in infants with flat head syndrome with no treatment. Therefore, they set out to do just that.
Use of a helmet as standard therapy 'discouraged'
For their research, they assessed 84 babies who had moderate or severe positional skull deformation. They had either plagiocephaly or brachycephaly.
From the age of 6 months, half of the infants were required to wear custom-made closely fitting helmets for 23 hours a day for a 6-month period. The remaining infants had no treatment at all.
On measuring the head shape of all infants once the babies reached 2 years old, the team found that the infants who wore the helmets showed no significant improvements, compared with those who received no treatment.
Helmet therapy led to 25.6% of infants making a full recovery from positional skull deformation, while 22.5% of infants who received no treatment made a full recovery - which the researchers deem as "no significant difference" between groups.
Side effects were reported by parents of the infants who wore the helmets. Around 96% of parents said their babies experienced skin irritation and 33% said they experienced pain. Approximately 77% of parents felt the helmet prevented them from cuddling their infants, 76% reported an unpleasant smell and 71% reported sweating.
When the infants were 2 years old, the researchers found that both groups of parents were generally happy with the shape of their child's head. The parents of those who wore the helmets reported a satisfaction score of 4.6 out of 5, while parents of children who received no treatment reported a satisfaction score of 4.4 out of 5.
Furthermore, the team notes the high costs of helmet therapy. On average, they found that the treatment cost around $1,935 (£1,157) per child.
Commenting on their findings, the researchers say:
"Based on the equal effectiveness of helmet therapy and skull deformation following its natural course, high prevalence of side effects, and high costs associated with helmet therapy, we discourage the use of a helmet as a standard treatment for healthy infants with moderate to severe skull deformation."
The researchers point out that in both groups, only 25% of babies made a full recovery. Therefore, they stress the importance of preventing babies from developing positional skull deformation.
They note that past research has indicated that babies should be placed on their tummy while awake. But they emphasize that while a baby is sleeping, the AAP guidelines - recommending that babies should be positioned on their back - should be followed.
In an editorial linked to the study, Prof. Brent R. Collett, of the University of Washington School of Medicine, says that it is important that parents are aware of the implications of helmet therapy and that future research involving larger samples of children would be useful to investigate further.
"In particular," he adds, "it would be of interest to learn whether children with the most severe positional plagiocephaly and brachycephaly, who were excluded from this trial, show meaningful improvement."