My baby has a flat spot on her head. what causes flat head and does it need treatment?

What the evidence says

A baby's skull is soft and pliable so it can be shaped by pressure. If your baby spends a lot of time with her head turned the same way, especially since babies sleep on their backs to reduce SIDS risk, one part of the skull can flatten. The Canadian Paediatric Society explains that a baby's skull is very soft and the bones can be affected by pressure, and that babies often turn their head to one preferred side when lying on their back, which is why flat spots develop.

This is called positional (or deformational) plagiocephaly, and it's very common - some estimates suggest up to a fifth or more of babies are affected. The good news: flat head from positioning does not affect brain development. Canadian guidance is clear that even more noticeable flattening will not affect a baby's brain or development, though it can affect appearance.

Many mild cases improve on their own once babies start moving more, rolling, and sitting up, taking pressure off the back of the head. Treatment depends on severity. For mild flattening, simple steps help: plenty of supervised tummy time while awake, alternating which end of the crib baby's head is at, changing the direction of toys/mobiles to encourage turning the head both ways, and limiting time in car seats or bouncers where the head rests on a flat surface.

If flattening is more pronounced or doesn't improve, your doctor may suggest counter-positioning techniques, or refer you to physiotherapy, especially if there is any neck tightness (torticollis) limiting head turning. For significant, persistent flattening not improving with repositioning by around 4-6 months, a referral for a custom-fitted helmet is sometimes offered, though evidence for how much helmets improve final outcomes (versus just speeding up improvement) is limited. One important thing to watch for: rarely, an odd head shape can be a sign of craniosynostosis, where the skull's growth plates fuse too early - a different condition that needs prompt medical assessment and sometimes surgery.

Signs that make doctors think of this rather than positional flattening include a head shape present at birth that is worsening rather than improving, or the ear on the affected side sitting further back rather than pushed forward. If you're ever unsure, get your baby's head shape checked by your doctor - it's usually diagnosed on exam alone, without imaging.