Flat head syndrome: causes, prevention and when to seek help

0-6 months · Health · Reviewed 20 June 2026 · All articles

A flattened area on a baby's head is one of the most common concerns raised at well-baby visits in the first six months of life. Positional plagiocephaly - flattening due to repeated external pressure on the skull - affects an estimated 20-46 percent of infants in some studies, with rates rising significantly since the early 1990s. For most families, the news is reassuring: the condition is usually mild, it does not affect brain development, and it typically resolves well with simple repositioning strategies started early. For a smaller proportion of babies, a referral for physiotherapy or helmet therapy may be appropriate. Understanding the difference, and knowing when to act, helps parents respond calmly and effectively.

What positional plagiocephaly is

The word plagiocephaly comes from the Greek for "oblique head." Positional or deformational plagiocephaly describes asymmetrical flattening of the skull caused by repeated mechanical pressure - the baby rests their head in the same position repeatedly, and over time the soft infant skull conforms to that pressure. The most typical pattern is a flat spot on one side of the back of the skull, often with forward shifting of the ear and forehead on the same side, giving an asymmetric appearance when viewed from above.

It is critically important to distinguish positional plagiocephaly from craniosynostosis, a separate and different condition in which one or more of the sutures (fibrous joints between skull bones) closes prematurely. Craniosynostosis restricts normal skull growth and requires surgical treatment. It is identified by a ridge along the affected suture, a specific and distinctive pattern of head shape abnormality, and the absence of a flat spot that changes with position. Craniosynostosis is uncommon (affecting approximately 1 in 2,000 births) and is typically diagnosed by physical examination and imaging. Positional plagiocephaly is much more common and has entirely different causes and treatment. This article addresses positional plagiocephaly only.

Brachycephaly: the other common flat-head pattern

Brachycephaly describes symmetrical flattening of the back of the skull on both sides equally, resulting in a head that is wide and short from front to back rather than asymmetric. It is caused by the same mechanism as plagiocephaly - prolonged supine positioning - and is managed in the same way. Some babies have elements of both brachycephaly and plagiocephaly simultaneously.

Brachycephaly can be harder to notice than plagiocephaly because it is symmetric and may not be obvious when looking at the baby from the front. It is often detected by a paediatrician during a routine well-baby visit or when looking at the baby's head from above or behind.

Why rates have increased since the Safe to Sleep campaign

Positional plagiocephaly was relatively uncommon before the early 1990s. The dramatic increase in prevalence since then is directly linked to the Back to Sleep (now Safe to Sleep) campaign, which was launched in 1992 in response to evidence that placing babies on their backs to sleep substantially reduces the risk of sudden infant death syndrome (SIDS). The campaign has been one of the most successful public health interventions in neonatal care, associated with a more than 50 percent reduction in SIDS deaths.

The tradeoff is that babies now spend more time with the back of their skulls in contact with surfaces. The infant skull is designed to be malleable in early life precisely to allow passage through the birth canal and rapid brain growth in the first year. This same malleability means that sustained pressure in one direction shapes the skull over time.

The solution is not to change sleep position - back sleeping remains the strongly recommended safe sleep position - but to increase the variety of head positions babies experience when awake and to actively incorporate tummy time and repositioning into daily care.

Risk factors

Several factors increase the likelihood of positional plagiocephaly.

Preterm birth: Preterm infants spend extended time in neonatal units where care needs often require a consistent supine position, and their skulls are proportionally softer than those of term infants. Plagiocephaly rates are higher in preterm infants.

Multiple gestation: Twins and triplets are more likely to have intrauterine positional constraints that predispose to head shape asymmetry at birth, which may persist or worsen after birth.

Torticollis: Congenital muscular torticollis is a condition in which one of the sternocleidomastoid muscles in the neck is shortened or tighter than the other, causing the baby to consistently tilt and rotate their head to a preferred position. Torticollis is strongly associated with plagiocephaly because the baby always rests on the same part of their skull. Torticollis may result from positioning in utero or from the use of forceps or vacuum during delivery.

Extended time in "containers": Car seats, bouncers, swings, and bouncy chairs all place the back of the baby's head in contact with a firm or semi-firm surface. These items are safe and useful for their intended purposes, but extended time in them beyond what is necessary for travel or supervised use increases the cumulative pressure on the skull. They should be seen as equipment for specific uses rather than as baby loungers for extended periods.

First-born status: First-born infants are statistically more likely to develop plagiocephaly, possibly because first-time parents are more cautious about tummy time, or because there is less carrying and more time in equipment.

Repositioning techniques

Repositioning is the first-line treatment for mild and moderate positional plagiocephaly and is effective for the majority of babies when applied consistently and started early.

Vary head position during sleep: Place the baby's head at alternating ends of the cot from night to night. Babies tend to turn toward visual stimulation in the room (light sources, activity, faces), so alternating which end the head is at means they alternately look left and look right. This distributes the pressure over both sides of the skull rather than always loading one side.

Encourage the baby to turn to the non-preferred side: Position the baby so that interesting things to look at - faces, light, movement - are on the side opposite the flat spot. If the flat spot is on the right, position the cot so the baby must turn left to see the room, the door, or the parents approaching.

Increase carrying time: Time spent being held upright in arms, in a baby carrier, or in a sling takes pressure off the skull entirely. A baby who is worn for several hours a day has substantially less contact time between skull and surface.

Reduce container time: Use car seats for travel, bouncers for brief supervised sessions, and avoid them as the default resting place. After travel, move the baby out of the car seat rather than leaving them to sleep in it.

Tummy time

Tummy time is the single most important active prevention strategy for positional plagiocephaly, and it also builds the neck, shoulder, and core strength that babies need to reach developmental milestones including rolling, sitting, and crawling. It must always be done while the baby is awake and under direct supervision - a sleeping baby should be returned to back sleeping immediately.

The AAP recommends starting tummy time from birth. In the first weeks, begin with very short sessions - 2 to 3 minutes, two to three times per day. This is enough to be beneficial while remaining manageable for the baby and parents. Gradually increase the duration as the baby gains neck strength and tolerance. By 3-4 months, aim for a cumulative total of at least 30 minutes per day spread across multiple sessions.

Many babies initially resist tummy time. Effective strategies to make it more tolerable include:

Consistency matters more than duration. Short, frequent sessions throughout the day are more effective and more tolerable than one long session.

When to see a doctor

Mild skull asymmetry in the first few weeks of life is extremely common and is often the result of the birth process - the skull is compressed during passage through the birth canal and typically rounds out within the first 4-6 weeks. This early asymmetry does not require intervention.

Seek medical advice if a flat spot is still clearly noticeable and not improving by 2 months of age, particularly if consistent repositioning has been in place. Early referral produces better outcomes than waiting.

Also seek review if your baby consistently turns their head to one side and resists or finds it difficult to turn to the other side - this is a sign of possible torticollis and warrants assessment. A paediatrician can assess the neck muscle tightness and refer for physiotherapy if needed.

Seek urgent assessment if you notice a hard ridge running along a suture line of the skull (rather than a soft flat area), if the head shape is rapidly changing, or if the fontanelle (soft spot) appears to be closing early. These are potential signs of craniosynostosis and require prompt evaluation.

Physiotherapy for torticollis

When torticollis is identified as a contributing factor to plagiocephaly, referral to a paediatric physiotherapist is an important part of treatment. The physiotherapist will assess the range of neck movement, identify which muscle is tight, and teach parents a programme of gentle passive stretching exercises to perform at home multiple times per day.

Stretching for torticollis involves gently moving the baby's head through its full range of motion to the non-preferred side and holding the stretch for a few seconds. Done consistently, this stretching gradually lengthens the shortened muscle. Most cases of congenital muscular torticollis respond well to physiotherapy when started in the first few months of life; cases started later or where tightness is more severe may take longer to resolve.

Physiotherapy for torticollis also indirectly addresses the plagiocephaly by freeing the neck to move symmetrically, allowing the repositioning strategies described above to be effective.

Helmet therapy (cranial orthosis)

Helmet therapy, also called cranial orthosis or moulding helmet therapy, involves having a baby wear a custom-fitted hard shell helmet for approximately 23 hours per day for a period of 3-6 months. The helmet is shaped to create a gap over the flat area of the skull and contact over the more prominent areas, gently guiding skull growth into a more symmetric shape as the baby grows.

Helmets are most effective when started between 4 and 12 months of age. Before 4 months, repositioning alone is often sufficient and the helmet fitting can be deferred to see whether the condition improves. After 12 months, skull growth slows substantially and the helmet is less effective at achieving reshaping. The window of maximum effectiveness is roughly 5-8 months.

The evidence base for helmet therapy is mixed. Several randomised controlled trials and systematic reviews have found that for mild to moderate cases, active repositioning and physiotherapy produce outcomes similar to helmet therapy by 24 months, with the skull shape largely normalising in both groups. Helmets are most clearly beneficial - and most reliably superior to repositioning alone - for moderate to severe cases where the degree of asymmetry is unlikely to resolve adequately through repositioning in the remaining window of skull plasticity.

The practical considerations are significant. Helmets require fitting by a specialist orthotist, typically at a clinic that specialises in cranial remoulding. The helmet must be adjusted as the baby grows, requiring regular clinic visits. The cost varies considerably by location and provider, and insurance or NHS coverage for helmet therapy varies. In many places, helmet therapy is not covered by public health systems for positional plagiocephaly (as opposed to craniosynostosis surgery), and the out-of-pocket cost can be substantial.

For families where a moderate to severe case is not responding to repositioning and the baby is within the appropriate age window, a referral to a specialist for assessment and measurement is a reasonable step that allows an informed decision based on the severity of the individual case.

Long-term outcomes

The long-term prognosis for positional plagiocephaly is generally excellent. As motor development progresses and babies gain the ability to roll, sit, and move independently, they naturally spend less time in any single position and the sustained loading on one part of the skull decreases. Most cases of positional plagiocephaly show substantial improvement over the first two years of life as a result of this natural process, combined with the effects of repositioning and physiotherapy.

Studies have found no association between positional plagiocephaly and cognitive development, language development, or other developmental outcomes. The brain grows normally inside the skull regardless of its external shape in deformational plagiocephaly. The concerns are cosmetic: head shape, facial symmetry, and in rare severe cases, possible effects on jaw or ear alignment.

A small residual asymmetry may persist in some cases but becomes progressively less visible as hair grows and head shape continues to fill out over the first few years. Most children have no noticeable asymmetry by school age.

Frequently asked questions

How much tummy time should my baby have?

The AAP recommends starting tummy time from birth, placing your baby on their tummy for short sessions several times a day while awake and supervised. Start with 2-3 minutes 2-3 times per day and gradually increase. By 3-4 months, aim for a total of 30 minutes per day spread across multiple sessions. Tummy time helps prevent flat head syndrome and builds the neck and shoulder strength needed for rolling and crawling.

When should I be concerned about my baby's head shape?

Some asymmetry in a newborn's head is normal and often due to the birth process; it usually resolves in the first few weeks. If you notice a persistent flat spot that is not improving by 2 months of age, or if your baby consistently turns their head to one side and cannot easily turn to the other, speak with your paediatrician. Early referral leads to better outcomes.

Does my baby need a helmet?

Most babies with positional plagiocephaly do not need a helmet. Consistent repositioning and tummy time resolve the majority of cases, particularly when started before 4 months. Helmets are typically recommended for moderate to severe cases that have not responded to repositioning after several months, ideally starting before 12 months while the skull is still rapidly growing and most responsive to gentle reshaping.

Will the flat spot affect my baby's brain development?

Positional plagiocephaly is a cosmetic condition affecting the shape of the skull, not the brain inside. The brain grows normally regardless of the skull's shape in deformational plagiocephaly. Studies have not found that plagiocephaly causes cognitive or developmental problems. The concern is purely about head shape, facial symmetry, and (in rare severe cases) jaw or ear alignment.