A flat spot is common in babies and is usually caused by pressure on the soft skull, especially after babies began sleeping on their backs. This pressure-related change is called positional plagiocephaly when one side looks flatter, or brachycephaly when the back of the head appears broad and flat. In most cases, it affects head shape rather than brain development, and back sleeping remains the safest position for every nap and nighttime sleep.
You’ll learn how torticollis, limited tummy time, and extended time in car seats or bouncers can add pressure, along with how doctors distinguish these changes from craniosynostosis. We’ll also cover safe prevention, warning signs, diagnosis, and treatment, including when repositioning, physical therapy, or baby helmet therapy may help. Never use pillows, wedges, or sleep positioners to change your baby’s head shape, and keep the crib firm, flat, and empty. Start with these tummy time activities for babies and learn which head-shape changes deserve a pediatric evaluation.
Watch: Flat Head – Tips to Avoid It
What Causes Flat Head Shape in Babies?
A baby’s skull is soft and flexible, with open sutures that allow the brain to grow. Because the bones can mold under steady pressure, a flat head shape often develops when one area rests against a mattress, car seat, swing, or bouncer for long periods.
Most cases are pressure-related changes in head shape, not signs of poor brain development. Babies should still sleep on their backs for every nap and nighttime sleep. Safe sleep matters more than trying to prevent a flat spot by changing sleep position.
Positional plagiocephaly creates a flat spot on one side
Positional plagiocephaly causes flattening on the back or back-side of the head, usually on one side. Parents may also notice mild facial asymmetry or an ear that sits slightly farther forward on the flatter side.
The main cause is repeated pressure in the same area. For example, a baby who regularly turns their head to the right during sleep and rest may place more pressure on the right back side of the skull. Over time, that pressure can change the shape of the soft bone.
Several factors can make this pattern more likely:
- Torticollis can tighten the neck muscles and make turning toward one side difficult.
- A baby may develop a strong preference for looking in one direction.
- Limited neck movement can keep the head in the same position.
- Long periods in car seats, swings, or bouncers can reduce opportunities to move freely.
Positional plagiocephaly usually affects the skull’s appearance rather than brain growth. Still, marked flattening, worsening asymmetry, or a shape that doesn’t improve deserves a medical assessment. A pediatrician can check the baby’s neck movement and head growth, then recommend appropriate treatment. You can also read more about positional plagiocephaly in babies.
Brachycephaly affects the back of the whole head
Brachycephaly causes more even flattening across the back of the skull. As a result, the head may look wider and shorter from above, rather than angled to one side. Some babies have both brachycephaly and plagiocephaly, so the back can look broad while one side remains flatter.
This pattern often develops when a baby spends extended periods lying on their back with little head movement. However, back sleeping should continue, because it remains the safest sleep position. During awake periods, supervised tummy time and free movement can reduce constant pressure on one spot.
Craniosynostosis is a less common structural cause
Craniosynostosis happens when one or more skull sutures close too early. Unlike positional flattening, which comes from outside pressure, craniosynostosis changes skull growth from within.
Possible clues include a firm ridge over a suture, a narrow or pointed skull shape, unusual head growth, or a shape that doesn’t follow a typical pressure pattern. The difference isn’t always easy to see, especially when a baby has facial asymmetry. A clinician must examine the head and track growth to tell these conditions apart.
Suspected craniosynostosis needs timely referral to a craniofacial or neurosurgical team. Early evaluation helps specialists identify the cause and decide whether treatment is needed. For additional medical background, the American Academy of Pediatrics explains infant head-shape abnormalities.
Which Babies Are More Likely to Develop a Flat Spot?
Some babies develop a flat spot more easily because they spend more time in one position or have less freedom to turn their heads. Risk factors can overlap, but one risk factor doesn’t prove it caused the flattening. Parents shouldn’t blame themselves. The practical focus is helping your baby move the head and neck comfortably during supervised awake time.
Torticollis can keep a baby facing one direction
Torticollis involves tightness or weakness in the neck muscles. As a result, a baby may struggle to turn the head equally in both directions. Repeated pressure then lands on the same area of the soft skull, which can contribute to positional plagiocephaly.
Watch for signs such as always looking toward the same side, tilting the head, or having trouble feeding comfortably on one side. A baby may also resist turning toward a particular direction during play or tummy time.
If you notice these patterns, discuss them with your pediatrician or a pediatric physical therapist. Don’t force the neck to turn, since gentle assessment and guided exercises are safer than trying to stretch it yourself.
Prematurity and limited movement can increase pressure
Premature babies may have softer skulls, less muscle strength, and fewer opportunities to move freely during the early weeks. Time spent in medical equipment or resting in one position can add to the pressure. Multiple births may also carry a higher risk because babies can have less room before birth or need extra medical support afterward.
Babies who haven’t started rolling, rarely move their heads, or have low muscle tone may also develop flattening more easily. However, slower rolling alone doesn’t mean something is wrong. Babies reach movement milestones at different times, and your pediatrician can assess muscle tone, head control, and overall development.
Research reviews list prematurity, multiple pregnancy, first birth, and torticollis among reported risk factors for positional plagiocephaly. Clinical research on positional plagiocephaly also shows why risk factors should be viewed as associations, not proof of personal fault. Firstborn babies and boys are sometimes reported to have higher rates, but those details aren’t actions parents can control.
Car seats, swings, and loungers add pressure outside the car
Car seats, swings, and loungers are useful for travel or short, supervised periods. Still, they shouldn’t become your baby’s main resting place while awake. Their curved surfaces can keep pressure on the back of the head and limit natural movement.
When you’re not traveling, move your baby to a firm, flat sleep surface when sleep is appropriate. During awake periods, offer supervised floor play, tummy time, and upright holding. These options give your baby more chances to turn the head and strengthen the neck.
The most helpful factors to address are head movement, neck mobility, and time spent lying on the back while awake. Safe back sleeping remains essential, so never use pillows, wedges, or positioning devices in the crib. For related movement guidance, see these tips on how tummy time supports sitting.
How to Prevent and Improve Positional Flat Head Safely
Prevention works best when you start early, but it should never come at the expense of safe sleep. Small changes during feeding, carrying, play, and awake rest can reduce repeated pressure on one area of your baby’s head. Keep placing your baby on their back for sleep, even if a flat spot has already appeared.
Keep back sleeping as the safest sleep position
Your baby should sleep on their back for every nap and overnight, on a firm, flat, non-inclined mattress with only a fitted sheet. The sleep space should remain empty. The American Academy of Pediatrics safe sleep recommendations do not support placing babies on their side or stomach to prevent a flat spot.
Never add pillows, rolled towels, wedges, sleep positioners, or soft head-shaping products to the crib. These items can cover your baby’s face, restrict movement, or increase the risk of suffocation and entrapment. Safe sleep guidance matters more than trying to keep pressure off the back of the head, so use these safe sleep practices consistently.
Use supervised tummy time while the baby is awake
Tummy time strengthens the neck, shoulders, and upper body while taking pressure off the back of the skull. Start with brief sessions and repeat them throughout the day. Gradually build toward about 30 minutes total each day, adjusting the amount for your baby’s age, strength, and tolerance.
Try chest-to-chest play while you’re fully awake, tummy time on a firm floor mat, or a small rolled towel under your baby’s chest for extra support. Stay close and watch your baby throughout the session. Stop when your baby becomes tired or distressed, and never use tummy time as an unsupervised sleep position. The NIH also recommends regular supervised tummy time to help prevent flat spots.
Change positions during feeding, carrying, and play
Alternate arms during bottle-feeding and carrying when it feels comfortable. During play, place your face or an interesting toy on the side your baby uses less often, encouraging gentle head movement without forcing it.
You can also change the direction your baby faces in the crib while keeping them on their back. For example, switch which end of the crib holds your baby’s head so the room, doorway, or your voice encourages looking in a new direction. Upright holding and supervised floor play add more opportunities for movement. These small adjustments spread pressure across the day.
Reduce unnecessary time in infant equipment
Use car seats for travel, not routine sleep or long periods of rest outside the vehicle. Swings, bouncers, loungers, and carriers can also hold your baby’s head in one position, especially when used for extended periods.
Follow each product’s safety instructions, and move your baby to an appropriate firm, flat sleep surface if they fall asleep in a device. When awake, offer floor play, tummy time, or upright cuddling instead. Free movement gives your baby more chances to turn the head and build neck strength.
How Doctors Tell a Flat Spot From Craniosynostosis
A pediatrician looks at the entire pattern rather than judging one flat area. Positional flattening usually follows repeated pressure and may improve as a baby gains neck control and moves more. Craniosynostosis develops when a skull suture fuses too early, which can restrict growth in a particular direction.
What a routine head-shape assessment includes
During the visit, the clinician measures head circumference and compares it with earlier measurements on the growth chart. A changing growth pattern can provide important information, so parents may find it helpful to review how pediatricians evaluate baby head size.
The clinician also examines the skull from above, behind, in front, and from both sides. They look for a typical pressure pattern, such as flattening on one back side, forward movement of the ear on that side, or mild forehead asymmetry. They gently feel along the skull sutures for a hard ridge or an unusual contour.
Next, they check whether the baby’s face and ears appear balanced and whether the head is growing as expected. A baby with positional plagiocephaly often has a recognizable pressure-related shape, while craniosynostosis may create a narrower, pointed, or otherwise unusual skull contour.
Neck movement matters, too. The clinician watches whether the baby turns freely in both directions and checks for signs of torticollis, which can keep pressure on one part of the skull. They also consider head control, muscle tone, feeding, and overall development.
Expect questions about:
- The baby’s usual sleep position and favorite head-turning direction.
- How much supervised tummy time the baby gets.
- Feeding positions and whether one side feels difficult.
- Prematurity, birth history, and time spent in car seats, swings, or bouncers.
- Changes in the head shape since birth or since the last appointment.
Bring dated photos or brief notes if the shape seems to be changing. They can help the clinician compare subtle changes over time.
Signs that deserve prompt medical review
Contact your pediatrician promptly if the head shape changes quickly, looks very unusual, or becomes severely uneven. A hard ridge along a skull suture, a pointed or narrow skull, or head growth that falls outside its expected pattern also deserves evaluation. You can review the clinical guidance on positional plagiocephaly for examples of findings that may need specialist referral.
A baby who cannot turn the neck both ways should also be assessed, especially when the head consistently tilts or faces one direction. Parents don’t need to diagnose craniosynostosis themselves. The examination usually provides the first answer, and imaging is not always needed for typical positional flattening. If the findings are unclear or suggest early suture fusion, the clinician may arrange imaging or refer the baby to a craniofacial specialist.
Breathing trouble, repeated vomiting, unusual sleepiness, seizures, or a baby who seems seriously unwell requires urgent medical care.
Treatment Options and When to Seek Help
Treatment depends on the cause, severity, baby’s age, and whether neck tightness limits movement. Mild positional flattening often improves as babies grow, roll, sit, and spend less time on their backs while awake. A clinician can monitor progress and recommend the right next step.
Repositioning and physical therapy are common first steps
For positional plagiocephaly or brachycephaly, care often starts with supervised tummy time, regular position changes, and more upright holding while your baby is awake. Limit unnecessary time in car seats, swings, bouncers, and loungers outside of travel or short supervised use. Continue placing your baby on their back for every sleep.
During play, place your voice, face, or a toy on the side your baby uses less often. You can also vary feeding and carrying positions when comfortable. These changes encourage natural head movement without interfering with safe sleep.
If torticollis or a strong movement preference is present, a pediatric physical therapist can teach safe stretches, positioning techniques, and exercises. Don’t force your baby’s neck to turn, and avoid copying stretches from unverified videos. Head-shaping pillows, wedges, and other unproven products can create safety risks and shouldn’t go in the crib.
Follow-up visits help track head circumference, neck movement, and changes in the skull’s shape. The Congress of Neurological Surgeons guidance on repositioning supports conservative treatment for deformational plagiocephaly.
When helmet therapy may be considered
A cranial remodeling helmet may be considered when flattening remains moderate to severe despite repositioning and physical therapy. It may help selected babies during a period of rapid skull growth, but helmet therapy isn’t needed for every baby. Mild cases often improve without it.
A qualified specialist should examine your baby, decide whether a helmet is appropriate, and determine the correct fit and wear schedule. Treatment works best when the helmet fits accurately and follow-up visits allow adjustments as the head grows. Johns Hopkins explains how helmet therapy works, including why infants need regular monitoring.
A helmet gently redirects skull growth. It doesn’t treat craniosynostosis in the same way surgery does, and it must not replace a medical evaluation when the skull shape seems unusual or continues to worsen.
Craniosynostosis needs early specialist care
Confirmed craniosynostosis is managed by a craniofacial or neurosurgical team. Treatment may involve surgery to create room for brain growth, improve skull shape, and address pressure inside the skull. The approach depends on which suture closed, the baby’s age, the skull’s shape, and the severity.
Early referral gives specialists time to confirm the diagnosis and choose the safest treatment plan. A suspected suture problem should not be treated with repositioning or a helmet alone.
When parents should call the pediatrician
Call your pediatrician if the flat spot is worsening, your baby always faces one direction, neck movement seems limited, or repositioning isn’t helping. Contact the office if you’re unsure whether the shape looks normal, even if your baby seems comfortable.
Routine monitoring is better than waiting for a severe change. Asking early is appropriate, and it doesn’t mean your baby has a serious condition.
Conclusion
Most flat head shapes in babies come from positional plagiocephaly or brachycephaly. Repeated pressure on a soft skull, limited movement, torticollis, or extended time in one position can cause flattening. Craniosynostosis is a separate and less common cause that needs medical assessment.
Keep placing your baby on their back for every nap and overnight sleep on a firm, flat, empty surface. A firm and flat bassinet sleep surface supports safe sleep. During awake periods, use supervised tummy time, vary positions, encourage head movement, and hold your baby upright to reduce constant pressure.
Ask your pediatrician about an unusual head shape, limited neck movement, abnormal head growth, or flattening that is getting worse. Early assessment can distinguish common positional changes from conditions that need specialist care, while guiding safe and effective treatment.
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