Brachycephaly in Babies: Flat Back of Head

Quick answer: Flat back of the head in babies (brachycephaly) is most often caused by prolonged back-lying. When the cephalic index exceeds 86, brachycephaly is defined. Mild cases improve with repositioning; moderate to severe cases are corrected with helmet therapy.

• First step: Sleep position changes + tummy time — effective when started before 4 months.
• Helmet therapy: Between 4–18 months; assessment with 3D scanning.
• Not craniosynostosis: If brachycephaly is positional, the sutures are open and it is not craniosynostosis.

Brachycephaly in babies is a medical term describing the flattening that parents notice at the back of their newborn's head. If, when you hold your baby or look down at them, you feel that the back of their head is flatter than usual and the sides appear wider, brachycephaly may be present. Do not worry; this is a common skull shape deformity worldwide and in our country, and it is manageable when detected early.

What Is Brachycephaly (Flat Back of Head) in Babies?

Brachycephaly derives from the Greek words for "short" (brachy) and "head" (cephal). It describes the symmetric flattening of the back of the baby's skull (the occipital region) with associated widening of the head to the sides. While plagiocephaly (oblique head) is an asymmetric deformity, brachycephaly in babies typically presents as a symmetric flattening.

This can cause the height of the baby's head to increase and the head to appear wider when viewed from the level of the ears. Parents often describe this as "my baby's head is very flat at the back."

What Are the Causes of Brachycephaly?

After birth, a baby's skull is very soft and pliable — both to protect a rapidly growing brain and to allow passage through the birth canal. This flexibility can leave the skull vulnerable to external pressure. The most common causes are:

• Back-Lying Sleep Position: The "Back to Sleep" campaign launched in the 1990s significantly reduced Sudden Infant Death Syndrome (SIDS). However, constant back-lying creates persistent pressure on the back of the skull, increasing the risk of flat back of head.
• Large Head Structure: Some babies have genetically larger or heavier heads. These babies may have difficulty turning their head to the side and may prefer to sleep lying consistently on the back.
• Low Amniotic Fluid: Reduced fluid in the womb can restrict the baby's movement, causing pressure on the back of the head.

How Do You Recognise the Signs?

You can notice the condition through simple observations at home. However, always consult a specialist for a definitive assessment.

• When you look at your baby from above, does the head shape appear more "round" or "square" rather than oval?
• Does the back of the head descend completely flat?
• Does the crown at the back of the head appear higher than normal?
• Is the width above the ears greater than usual?

Supportive Methods and Helmet Therapy

In mild cases, carrying out tummy time activities when the baby is awake and changing the sleep position (with medical guidance) can contribute positively to the process. However, in moderate to severe cases of brachycephaly in babies, positioning alone may not be sufficient.

At this point, a cranial orthosis — that is, helmet therapy — comes into play. Helmet therapy gently holds the widening sides of the skull, helping to direct growth towards the flattened back. This is a passive guidance method; the helmet does not compress the skull, it simply guides the direction of growth.

At CranioWell, we measure your baby's head shape to the millimetre using 3D scanning methods and map out the most appropriate path for you. For detailed information about the process, you can reach us via our Contact page.

Frequently asked questions

Does brachycephaly cause intellectual disability?

No. Brachycephaly is not a neurological condition that directly affects brain development or intelligence. It is a morphological (deformational) skull shape disorder.

When does flat back of head in babies resolve?

When babies begin to roll and sit (around 6 months), the pressure on the back of the head decreases. In mild cases, improvement may be observed during this period. However, it is important to intervene before the skull bones harden (within the first 18 months).

Does helmet therapy cause discomfort?

Modern cranial orthoses are made from lightweight and breathable materials. Babies typically adapt fully to the helmet within 1–2 days and continue their daily activities without any problems.

Conclusion and Recommendation

If you are wondering whether the flattening at the back of your baby's head is temporary or requires intervention, the healthiest course of action is to seek specialist advice without delay. At CranioWell Orthopaedic Centres, you can have your baby's head index measured at a free initial assessment.

Related: repositioning therapy for babies.

Frequently Asked Questions

When is helmet therapy needed for brachycephaly?

Helmet therapy is generally considered in babies aged 4–18 months with moderate to severe brachycephaly. The ideal starting age is 4–6 months; the skull grows most rapidly during this period and the helmet's guiding effect is at its strongest. The decision is made by measuring the cephalic index and CVAI with 3D scanning.

Does brachycephaly resolve on its own?

Mild brachycephaly largely improves within the first 4 months with sleep position changes and tummy time. However, for cases beyond 6 months and of moderate to severe degree, complete resolution without helmet therapy should not be expected. Early assessment cannot recover time already lost.

What is the difference between brachycephaly and plagiocephaly?

Brachycephaly is the bilateral flattening of the back of the head (wide, short head); plagiocephaly is unilateral flattening with facial asymmetry. The two can occur together — this is called "asymmetric brachycephaly" or "plagiocephaly + brachycephaly".