Flat Head Syndrome (Positional Plagiocephaly): Causes, Prevention, Treatment

You've been diligently following the advice to put your baby to sleep on their back — and now you're noticing a flat spot developing on the back of their head. The irony is real: the lifesaving recommendation to sleep on the back to prevent SIDS has also contributed to a significant rise in positional plagiocephaly. The good news is that for most babies, it's a cosmetic issue that responds well to simple, consistent repositioning — and doesn't affect how their brain develops.

What Is Positional Plagiocephaly?

Positional plagiocephaly (from the Greek: "plagios" = oblique, "kephalē" = head) is asymmetrical flattening of the skull caused by external pressure. Because babies' skull bones are soft and malleable in the first months of life, prolonged pressure in one area reshapes the bone.

The most common pattern: A flat spot on one side of the back of the head (called unilateral occipital plagiocephaly). This typically develops when a baby consistently turns their head to one preferred side — often due to mild neck muscle tightness (torticollis).

Brachycephaly: When flattening affects the entire back of the head symmetrically rather than one side. Associated with babies spending most time lying flat on their backs overall.

Source: AAP Clinical Report on Prevention and Management of Positional Skull Deformities

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Why Positional Plagiocephaly Has Increased

Since the AAP launched the "Back to Sleep" (now "Safe to Sleep") campaign in 1992, SIDS deaths have dropped by more than 50%. The same campaign, however, has more than doubled the prevalence of positional plagiocephaly — because babies who sleep safely on their backs also spend prolonged time with their heads resting on firm surfaces.

Compounding factors:

• Babies spend more time in car seats, bouncers, and swings (all supine)
• Shortened hospital stays mean positional habits can develop early without parental awareness
• Many parents aren't taught the importance of tummy time from the first week

The balance: Continue safe sleep practices without question. Simply offset supine time while awake with supervised tummy time.

Prevention: It Starts from Week One

Tummy time while awake and supervised is the single most effective prevention tool. Tummy time:

• Relieves pressure from the occiput (back of the head)
• Strengthens neck, shoulder, and core muscles
• Reduces torticollis risk by encouraging active head turning in both directions

Target at least 30 minutes of total tummy time per day by 2 months, broken into short sessions starting from birth.

Source: AAP tummy time recommendations

Additional prevention strategies:

• Alternate head position when placing baby down — one night facing left, next facing right
• Change orientation in the crib so the baby turns toward different stimuli (lights, sounds, faces)
• Minimize time in car seats/bouncers when not in a moving vehicle
• Carry and hold more — upright carrying eliminates all pressure on the skull

When to Suspect Torticollis

Many cases of plagiocephaly are caused by or worsened by congenital muscular torticollis — tightness in the sternocleidomastoid (SCM) neck muscle that causes the baby to consistently turn their head to one side.

Signs of torticollis:

• Baby consistently turns head to prefer one direction
• Head tilts to one side
• Visible tightness or a small lump in the neck muscle
• Difficulty turning head fully in both directions

Torticollis responds well to infant physiotherapy (gentle stretching exercises). If you notice that your baby strongly prefers one head position, ask your pediatrician for a referral to a pediatric physiotherapist. Treating torticollis usually resolves the plagiocephaly that was caused by it.

Helmets: Who Needs One?

Cranial remolding orthoses (helmets) work by applying gentle, consistent pressure to the prominent areas of the skull while creating space for the flat area to round out. They're worn 23 hours per day.

When helmets are typically recommended:

• Moderate to severe plagiocephaly (measured objectively using a cephalic ratio or cranial vault asymmetry index) that has not improved with 2–3 months of consistent repositioning
• Best outcomes when started between 4–6 months of age
• Minimal benefit when started after 12 months

What to expect: Helmet treatment typically lasts 3–6 months. Results are good in babies who start early and comply with wear time.

When to Call Your Doctor

Make an appointment to discuss head shape at the next well-child visit if:

• You notice a flat spot before 6 weeks of age
• The flat area isn't improving after 2–3 months of consistent repositioning and tummy time
• You suspect your baby has torticollis (head consistently turning to one side)
• You feel a hard ridge along a suture line on the skull

See your pediatrician promptly if:

• Head circumference growth appears to have stopped or slowed significantly — see baby soft spot and fontanelle for related warning signs to monitor at home
• Your baby's head shape seems unusual from birth, not developed over weeks
• You notice facial asymmetry developing

The vast majority of positional plagiocephaly cases improve significantly — or completely — with repositioning, tummy time, and time. Starting early (the first 2–3 months) gives the best results, but even babies who start repositioning at 4–5 months often see meaningful improvement. For technique and timing guidance on the single most effective repositioning tool, see tummy time for babies.