A flat spot developing on an infant’s head, medically known as positional plagiocephaly or brachycephaly, is a common occurrence. This condition results when the baby’s malleable skull develops a flattened area due to consistent external pressure. Understanding the different stages of skull development and the appropriate interventions for each stage can provide a clear path forward.
Understanding Positional Head Flattening
Positional flattening results from consistent external forces on the soft, rapidly growing skull. Plagiocephaly involves an asymmetrical flattening on one side of the back of the head, often causing the ear and forehead on that side to appear slightly pushed forward. Brachycephaly, in contrast, presents as a symmetrical flattening across the entire back of the head, making the head appear wider than usual.
The primary cause is the prolonged time infants spend lying on their backs, a necessary practice to reduce the risk of Sudden Infant Death Syndrome. This constant pressure leads to deformation. This common and treatable condition must be distinguished from craniosynostosis, a rare, more serious condition where the skull’s bony plates fuse prematurely and require surgical intervention.
The Critical Window for Skull Correction
The most important factor in correcting a flat head is skull plasticity—the period when the bone structure is softest and growing most rapidly. During the first six months of life, the infant’s brain undergoes a massive growth spurt, making the skull especially responsive to changes in pressure and position. This 0-to-6-month period is the optimal time for the most rapid and effective non-invasive correction.
Correction becomes progressively slower after six months as the rate of skull growth decreases. As the infant gains mobility, the window for easy, significant correction narrows. The bones also gradually begin to harden, meaning more aggressive intervention may be required to achieve the same level of change seen earlier.
Specific Intervention Options and Age Limits
For infants up to about four to six months of age, the first line of intervention is repositioning and increased Tummy Time. Repositioning involves consistently changing the head’s orientation while the baby is asleep or resting to relieve pressure on the flattened area. Parents should maximize supervised time the baby spends on their stomach while awake to promote muscle development and take pressure off the back of the head.
When repositioning efforts are insufficient, particularly in moderate to severe cases, a physician may recommend a cranial orthosis, commonly known as helmet therapy. This custom-fitted helmet applies gentle, persistent pressure to the prominent areas of the skull while allowing the flat areas to grow into the empty space. The optimal window for initiating helmet therapy is between four and eight months of age, capitalizing on the remaining rapid growth of the skull.
The age at which it is considered “too late” for this effective non-surgical intervention is usually around 14 to 18 months. By this age, the skull’s growth rate has slowed dramatically, and the bone plates have hardened substantially, making the helmet far less effective at redirecting growth. Starting treatment before nine months old is associated with a significantly higher rate of successful correction.
Long-Term Outcomes of Late Diagnosis
For infants who pass the optimal intervention window, or whose condition is mild, the prognosis remains largely positive. Positional head flattening is primarily a cosmetic issue and does not generally affect a baby’s brain growth or neurological development. This condition is fundamentally different from craniosynostosis, which can restrict brain growth.
As a child grows and their hair grows in, minor residual flattening often becomes visually less noticeable. The skull continues to slowly remodel and facial structures mature, which can further obscure any remaining asymmetry. The consensus is that the head shape malformation itself is not a direct cause of developmental delays.