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Promoting tummy time is one way to prevent flattening of the back of the baby's skull. (iStock)

Almost half of Canadian infants develop flat areas on the back of their heads by the age of two months, likely the result of sleeping face-up to prevent sudden infant death syndrome, a study suggests.

The study by Calgary researchers is believed to be the first in Canada to look at the incidence of what's known as plagiocephaly, a flattening of the back of a baby's skull.

"What we found out was that when we studied infants that were seven to 12 weeks of age coming into two-month immunization clinics in Calgary, almost half of them had some sort of flat spot on their head," said Aliyah Mawji of the school of nursing at Mount Royal University in Calgary.

"That was pretty surprising. I didn't anticipate that it would be that high."

Plagiocephaly occurs because the bony plates of a baby's skull are soft and have not yet fused together. This flattening at the back of the head — typically on one side or the other, based on how the infant lies — can cause facial and other changes.

"If they've got a flat spot on one side, what that likely means is that they've got the forehead protrusion on the same side and they also have a bit of ear shifting forward on the same side," said Mawji.

While the distortions are cosmetic and rarely cause a medical problem, left untreated they can become permanent and affect the child later in life.

"I would assume that if you've got a child that looks a little bit different than some of the other kids in their class, they might be at risk for bullying," she said. "Because you've got the chin that points in the other direction, you've got some shifting of the nose and the ears and the eyes and the forehead.

"They're going to look a little bit different. So we do need to be careful about that."

Vary baby's head position for sleep

The study, published in Monday's issue of the journal Pediatrics, involved 440 infants aged seven to 12 weeks who were assessed for plagiocephaly during well-baby visits at four Calgary community health centres in 2010.

Researchers found that 205 — or 46.6 per cent — had some head-flattening. Almost two-thirds were affected on the right side of the back of the skull and almost 80 per cent had a mild form of the condition.

Only a few of the infants had flattening on both sides of the back of the head, a condition called brachycephaly.

Mawji said newborns often have some flat spots on their skulls as a result of their position in the womb or from pressure during vaginal birth, but this usually resolves at about six weeks of age.

Flat spots that persist are usually caused by how the child lies during sleep, activities during waking hours and feedings.

"So if the baby is constantly placed in the same position, so either the same feeding position or the same sleeping position or being left in car seats or bouncy swings, we see more of what we call the positional plagiocephaly," Mawji said.

While the condition can be treated with specially fitted helmets, parents can take a few simple steps to prevent their baby's head from becoming misshapen, she said.

Car seats for transport only

"The first thing that's really important is to continue putting their babies to sleep on their back. We don't want people changing their position of sleep … because that would increase the chance that they would have sudden infant death syndrome.

"But make sure that you're varying the side of the head that the baby is turning to. So, for example, if you're putting your infant to sleep on their back and they automatically turn their head to the right, because that's comfortable for them, the next night what you want to do is turn their head to the left, and then alternate back and forth.

"And that should help prevent the position of just the one flat spot on one side of the head."

Mawji said parents should also make sure that babies are not left too long in devices such as car seats or bouncy swings that put pressure on their skulls and can contribute to flattening.

"What we recommend is only putting your infant in the car seat for travel purposes. When you get to your destination, you need to take your infant out of that car seat," she said. "Same for a bouncy swing — get a different type."

Moms also should avoid holding their baby with the same arm for breast or bottle feeding, and alternate arms from one feeding to the next, she said.

"Another thing that parents can do is promote tummy time, even when your baby's a week old, that's not too soon to start. So lay the baby on its tummy, awake and supervised. It helps build muscle strength in the neck and shoulders and arms.

"That will help the baby reach their developmental milestones, which is really important, and it also keeps the baby off their head," Mawji said, advising that infants be put on their bellies for a few minutes with every diaper change.

Steps such as these can prevent the need to have a child fitted with a helmet. These devices work by reshaping the skull over time, but they need repeated adjustments as the baby's head grows and are also expensive.

A helmet typically runs between $1,000 and $3,000, and many children outgrow the first device and will need to be refitted with a second one to reshape their heads properly. As most provincial health insurance plans don't cover the cost, parents must pay out of pocket, she said

Knowing how common the condition is among Canadian infants is important "because it has a huge impact on our health-care system," she said. "If you look at head shape clinics across Canada, currently some of them have a six- to eight-month wait.

"So you want to be able to prevent this or catch it early."