Flat Head Syndrome (Plagiocephaly): Preventing and Correcting It Safely

You lift your baby out of the bath and notice that one side of the back of their head looks flatter than the other. Or a grandmother points it out and suggests a little pillow to "round off" the skull. Plagiocephaly, or flat head syndrome, is common in young babies. It is harmless for the brain, and the earlier you act, the better it can be prevented and corrected.

Above all, it is not fixed with a pillow, or by changing the sleeping position. Here is what happens, the habits that really work, what is dangerous, and the role of the physiotherapist.

What is plagiocephaly?

It is a change in the shape of the skull that develops after birth because of repeated pressure, without any abnormal fusing of the bones. The French health authority (HAS) calls it "positional skull deformity". There are two main forms:

• plagiocephaly: the back of the head is flattened on one side only. Seen from above, the head looks lopsided, the ear on the flat side sits further forward, and the forehead may bulge on the same side;
• brachycephaly: the back of the head is flattened evenly on both sides. The head looks wide and short.

The NHS points out that this is common in young babies and causes no other symptoms. Neither the brain nor development is affected.

Why does a baby's head flatten?

A newborn's skull is very soft, and its bones can change shape under pressure, explains the Canadian Paediatric Society. Their neck muscles are weak: lying on their back, they often turn their head to the same side every time.

The main factor, according to the HAS, is a lack of freedom to move: a baby who spends long hours held still in a bouncer, a car-seat shell, a positioning wedge or a very tight swaddle keeps pressing on the same spot. The HAS also cites:

• prematurity, a twin pregnancy, a breech position, or a forceps or vacuum delivery;
• torticollis (a stiff neck), which makes baby look to the same side all the time;
• a lack of stimulation or interaction, or a mobile always hung in the same place.

Always on the back to sleep

This is the one non-negotiable point. Sleeping on the back protects against sudden unexpected infant death. A flat head never justifies putting baby to sleep on their tummy or side, stress the HAS, the NHS and the Canadian Paediatric Society.

The HAS recalls the rules: on the back, in a suitable cot, on a firm mattress, in a baby sleeping bag, with no pillow, duvet, bumper, comforter or soft toy. It is all explained in our article on safe sleep and sudden infant death.

So preventing a flat head happens while baby is awake.

Habits that prevent a flat head

Tummy time, awake and supervised. This is the key habit. The Canadian Paediatric Society aims for 10 to 15 minutes at least 3 times a day, always with an adult watching. The HAS suggests starting gently, at nappy changes. These moments also strengthen the neck and back. A play mat on the floor is all you need.

Alternate sides. At each breastfeed or bottle, switch arms: baby will turn their head to look for your eyes (HAS). Lay them with their head at the top of the cot one day, at the foot the next (HAS, Canadian Paediatric Society). Vary the position of toys and the mobile so they look both ways.

Carry them often. The HAS recommends carrying, in your arms or in a wrap, always keeping their face clear. A well-adjusted ergonomic baby carrier takes the pressure off the back of the skull. Safety rules are in our guide to baby carriers and wraps.

Limit time in equipment. The HAS asks you to limit time in the bouncer, rocker or car-seat shell as much as possible, and to keep the car seat for the car. The NHS advises taking baby out of the car seat as soon as you arrive.

Let them move. On the floor, on a mat, baby turns their head, wriggles and discovers their hands. This is the principle of free movement, which the HAS promotes. Our baby activity ideas give suggestions month by month.

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Head wedges and anti-flat-head pillows: why the HAS says no

Head wedges, baby positioners, positioning pillows, cot bumpers, "anti-flat-head" pillows, memory-foam mattresses: these items are often offered to worried parents. The HAS is unambiguous: such restraining equipment is "useless, harmful and dangerous".

Useless, because it does not prevent a flat head: by keeping baby still, it works against the freedom of movement that prevents it. Dangerous, because it makes it easier for baby to roll onto their tummy and raises the risk of death by suffocation. So in baby's cot, you put nothing. Outside the cot, no pillow replaces tummy time and your arms.

Torticollis: when baby always turns their head the same way

A baby who always looks to the same side, has trouble turning their head, or holds it tilted may have torticollis. The HAS distinguishes:

• postural torticollis, which comes and goes: you can gently turn baby's head to the other side with no resistance;
• congenital muscular torticollis, which is permanent: rotation is limited.

The doctor checks for it simply: a baby without torticollis turns their head both ways to keep eye contact with a parent. When neck mobility is limited, the HAS asks for physiotherapy to be systematically prescribed, as early as possible: care started in the first month gives the best chance of recovery. The physiotherapist also teaches you gentle exercises to repeat at home, adds the NHS.

Physiotherapy, osteopathy, helmet: what is offered if the head stays flat?

• Repositioning advice described above remains the foundation, at any age.
• Physiotherapy is indicated as soon as there is limited neck mobility (HAS).
• Osteopathy: according to the HAS, current data do not allow it to be recommended. At best it can support physiotherapy, as a second choice.
• The helmet (cranial orthosis): the HAS sees it as exceptional, and it can only be prescribed by a team specialised in skull and facial malformations. The NHS does not offer it, for lack of sufficient evidence that it works.

If the shape does not improve despite appropriate care, the HAS recommends referring baby early, towards the end of the first six months, to a specialised centre. Positional deformities have "a good prognosis", it concludes. Check-ups, such as the one for your baby at 2 months, are good moments to raise it.