What Is Flat Head Syndrome?

Flat head syndrome usually appears when a baby spends the early months sleeping with the head turned the same way. That can flatten one side or the back of the head.

Flat head syndrome is also called positional plagiocephaly.

What Causes Flat Head Syndrome?

The most common cause is sleep and resting position. Babies spend many hours on their backs, so one spot on the skull can flatten. The same pressure can occur in car seats, carriers, swings, and bouncers.

Premature babies are more likely to develop flattening. Their skulls are softer than those of full-term infants. Time in a neonatal intensive care unit can add risk because babies may lie on their backs for long periods with less handling.

Flattening can also begin before birth if the skull is pressed by the mother’s pelvis or by a twin. Many babies from multiple pregnancies are born with some flattening.

Neck muscle tightness that makes turning difficult—torticollis—can also contribute. Because turning is hard, babies tend to keep the same head position while lying down, and flattening can develop.

Once one side is already flat, torticollis can worsen: turning away from the flat side takes more effort, so the baby stays on that side and the neck stiffens further.

Signs of Flat Head Syndrome

Parents often notice these signs:

• The back of the head is flatter on one side.
• There is often less hair over the flat area.
• From above, the ear on the flat side may look pushed forward.

In more advanced cases the forehead opposite the flattening can look fuller or uneven. If torticollis is present, the neck, jaw, and face may also look asymmetric.

How Is Flat Head Syndrome Diagnosed?

Clinicians can usually diagnose flat head syndrome by examining the head. They may watch how the baby moves the head and neck to check for torticollis. Imaging is often unnecessary.

How Is Flat Head Syndrome Treated?

To reduce Sudden Infant Death Syndrome (SIDS) risk, infants should sleep on their backs—not on the stomach. Back sleeping can increase the chance of positional flattening.

When flattening is related to resting position, families can help by varying positions, holding the baby more often, and offering supervised tummy time. Useful steps include:

• Practice tummy time. Give supervised awake time on the tummy during the day. See our tummy time guide for details.
• Tummy time supports more even rounding at the back of the head.
• It also helps babies explore and learn about their surroundings.
• It strengthens neck muscles and helps babies push up on the arms—skills that support sitting and crawling.
• Change crib orientation. Many right-handed parents carry babies on the left arm and place them with the head to the left, so the baby turns right to look into the room. Switching sides encourages active turning toward the rounder side.

• Hold your baby more often. Limit long stretches with the head against a flat surface (car seats, strollers, swings, bouncers, play mats). If your baby falls asleep in a car seat, move them out once you arrive home rather than leaving them to nap there. Holding reduces pressure on the skull.
• Alternate head position during sleep. While the baby sleeps on the back, alternate left and right head placement. Even if the baby moves overnight, start with the rounder side down and the flatter side up. Do not use wedges or devices that lock a baby in one position.
• Use physiotherapy and home exercises. Many babies with flat head syndrome also have some torticollis, so physiotherapy and a home stretching program are often part of care. A physiotherapist can teach stretches that lengthen the tight side of the neck over time. Exercises are simple but should be done correctly.
• Helmet therapy may be considered. A physician may recommend a cranial remolding helmet when measurements show asymmetry above a clinically relevant threshold. The helmet sits looser over flatter areas and closer over fuller areas so growth is guided into flatter zones. Fitting of the HKM Pro helmet is provided only at CranioWell Orthotics & Prosthetics Centers. Discuss with your clinician whether a helmet is appropriate for your baby.

What Else Should Families Know?

Flat head patterns often improve partly with time and natural growth. As babies begin to change position in sleep, the head is no longer held in one place.

Once babies can sit independently, flattening usually stops progressing. Over months and years, even more noticeable flattening can soften as the skull grows. As hair thickens in the first years, a flat spot often becomes less visible.

Positional flat head syndrome does not affect brain development. Neck tightness, however, can slow early motor progress. Physiotherapy for torticollis should include checking developmental progress and adding exercises if delays appear.