Most babies develop some degree of head flattening in the first few months of life, and in nearly all cases, it rounds out on its own with simple changes to how you position your baby throughout the day. A large cohort study published in Pediatrics found that almost 47% of infants between 7 and 12 weeks old had some form of positional flattening, with about 78% of those cases being mild. So if your baby’s head doesn’t look perfectly round, you’re far from alone, and there’s a lot you can do about it.
Why Baby Heads Flatten in the First Place
Infant skulls are soft and made up of separate bone plates that haven’t yet fused together. This flexibility is what allows babies to pass through the birth canal, but it also means their heads are easily molded by outside pressure. When a baby spends a lot of time lying on the same spot, that area can gradually flatten.
There are two common patterns. One-sided flattening, called plagiocephaly, happens when a baby consistently turns their head to the same side during sleep. The back of the head on that side becomes flat, and sometimes one ear shifts slightly forward. Symmetric flattening across the entire back of the head, called brachycephaly, creates a wider, shorter head shape. Both are caused by the same basic thing: sustained pressure on one part of the skull.
The rise in back-sleeping, which is essential for reducing the risk of sudden infant death, has made positional flattening much more common. That’s an important trade-off to understand: a slightly flat head is a cosmetic issue that resolves, while unsafe sleep positions carry serious risks.
Repositioning Techniques That Work
The most effective thing you can do is vary where pressure falls on your baby’s head throughout the day. The American Association of Neurological Surgeons recommends several specific strategies:
- Alternate crib orientation. Every few days, switch which end of the crib your baby’s feet point toward. Babies naturally turn their heads toward the room’s activity, the door, or the window, so changing their position in the crib changes which side of the head bears weight.
- Switch sides during feeding. Whether you’re breastfeeding or bottle-feeding, rotate your baby’s head position from side to side between feedings so the same spot isn’t always pressed against your arm.
- Hold your baby upright. Frequent “cuddle time” with your baby held upright over your shoulder takes all pressure off the back of the skull. The more awake time your baby spends off the back of their head, the better.
- Avoid pressure on the flat side. When carrying or holding your baby, be conscious of not pressing on the area that’s already flat. Position them so the rounded side bears more contact.
- Move the crib in the room. Shifting the crib’s location so your baby has to look a different direction to see interesting things (a window, the door, your face) encourages natural head turning.
These changes are most effective in the first four to five months, when the skull is most malleable and babies spend the most time on their backs.
How Much Tummy Time Your Baby Needs
Tummy time is the single most important daily habit for rounding out a baby’s head. When your baby is on their stomach during awake, supervised play, no pressure is hitting the back of the skull at all. It also strengthens neck, shoulder, and core muscles, which eventually helps your baby hold their head up and move it freely.
The NIH recommends starting with two or three short sessions of 3 to 5 minutes each day for newborns. By around 2 months, the goal is 15 to 30 minutes of total tummy time daily, spread across multiple sessions. As your baby gets older and stronger, sessions can get longer and more frequent. Many babies fuss during tummy time at first. Getting down on the floor face-to-face with them, using a rolled towel under their chest for support, or placing a small mirror in front of them can help.
Check for Neck Tightness (Torticollis)
If your baby strongly prefers turning their head to one side, the cause may not just be habit. A condition called congenital muscular torticollis involves tightness in one of the neck muscles, causing the head to tilt one way while the chin points the other direction. Torticollis and head flattening often go hand in hand: the tight muscle keeps the baby’s head locked in one position, and that constant pressure creates a flat spot.
Signs to watch for include your baby always looking the same direction, resisting when you try to turn their head, or a visible head tilt. If you notice these patterns, a pediatrician can check for torticollis and refer you to a physical therapist. Treatment typically involves gentle stretching exercises to loosen the tight muscle, combined with positioning strategies and extra tummy time. Catching it early makes a significant difference, both for neck mobility and for preventing further flattening.
Always Keep Back-Sleeping for Sleep
It can be tempting to let your baby sleep on their side or stomach to take pressure off a flat spot, but this is not safe. The CDC and the American Academy of Pediatrics are clear: babies should be placed on their backs for every sleep, including naps. The sleep surface should be firm and flat (not angled or inclined), with no pillows, blankets, bumper pads, or soft toys.
Head shape improves with daytime repositioning and tummy time. Sleep time should remain strictly on the back, on a bare firm surface. The flattening is temporary. The risks of unsafe sleep positions are not.
Don’t Use Head-Shaping Pillows or Positioners
Products marketed as “baby head-shaping pillows” or infant sleep positioners may seem like an easy fix, but the FDA has issued explicit warnings against them. The agency is aware of infant deaths linked to these products over the years. Babies can suffocate after rolling onto their stomachs within the positioner, or become trapped between the device and the side of the crib.
The FDA states that no currently available baby product has been shown to prevent or reduce the risk of SIDS, and it discourages consumers from buying any product making such claims. This includes wedge-style positioners, bolster pillows, and any device designed to hold a baby in a specific position during sleep. Repositioning your baby by hand and increasing supervised tummy time are both safer and more effective.
When Helmet Therapy Comes Into Play
For moderate to severe flattening that hasn’t responded to repositioning, a pediatrician may recommend a cranial orthosis, commonly called a helmet. These custom-fitted helmets work by leaving space where the skull needs to grow while gently guiding growth away from the areas that are already prominent.
Doctors assess severity by measuring the diagonal difference between the two sides of the skull. A difference of 9 to 12 millimeters is considered mild to moderate, while anything over 12 millimeters is classified as severe. A related measurement called the cranial vault asymmetry index flags severe cases when it exceeds 3.5.
Timing matters with helmets. They work best when started between 4 and 6 months of age, while the skull is still growing rapidly. After about 12 months, skull growth slows considerably and helmets become less effective. Most babies wear the helmet for 2 to 4 months, typically 23 hours a day. The process is painless for the baby, though it requires commitment from parents.
The vast majority of babies never need a helmet. Consistent repositioning and tummy time resolve most cases of flattening well before the helmet conversation becomes relevant. But if your baby’s head shape isn’t improving by 4 months despite your efforts, that’s the right time to ask your pediatrician about a formal assessment.