Flat Head (Plagiocephaly) in Babies

Content reviewed against published AAP, AAP, NHS guidelines

Editorial policy

Last reviewed:

Positional plagiocephaly is a flattening of one side of a baby's head, or brachycephaly is flattening at the back. It is very common, affecting up to 47% of infants, and typically results from spending time in one position. It is usually cosmetic and improves with repositioning, though severe cases may require a helmet.

Key takeaways

  • Positional plagiocephaly is a flattening of one side of a baby's head, or brachycephaly is flattening at the back.
  • Most common cause: Positional preference (always sleeping in same direction)
  • Emergency: Head shape abnormality noted at birth with visible ridge along suture (possible craniosynostosis)
  • Home care: Supervised tummy time starting from birth — aim for 30-60 minutes total per day by 3 months

Possible Causes

Positional preference (always sleeping in same direction)common
Back sleeping position (safe but can cause flattening)common
Torticollis (tight neck muscle limiting head rotation)common
Premature birth (softer skull bones)uncommon
Multiple birth (limited space in utero)uncommon
Craniosynostosis (premature fusion of skull sutures)rare

When to Seek Help

Emergency — Call 911 or go to ER:

  • Head shape abnormality noted at birth with visible ridge along suture (possible craniosynostosis)
  • Rapidly changing head shape with signs of increased intracranial pressure (bulging fontanelle, vomiting)

Urgent — See doctor today:

  • Severe asymmetry with facial features affected (ear misalignment, forehead prominence)
  • Baby cannot turn head to one side at all (significant torticollis)

Same-day appointment:

  • Moderate flattening that is worsening despite repositioning efforts
  • Concern about possible craniosynostosis (ridge felt along skull)

Monitor at home:

  • Mild positional flattening with good head rotation to both sides
  • Flattening that is stable or improving with repositioning and tummy time
  • Baby under 4 months with common back-of-head flattening

By Age

0-2 months

Normal: Some head molding from birth is normal and resolves within weeks. Slight flattening from back sleeping is very common and typically not concerning at this age.

Worry if: A ridge along a suture line, very abnormal head shape present at birth, or rapidly worsening asymmetry. These could indicate craniosynostosis.

2-4 months

Normal: This is the peak age for developing positional plagiocephaly as babies spend most time on their backs. Mild flattening is extremely common.

Worry if: Severe asymmetry with facial features shifting (ear or forehead misalignment), or baby unable to turn head to one side (possible torticollis). Mention at well-visit.

4-8 months

Normal: Once baby starts rolling and spending more time upright, the head shape often begins to improve naturally.

Worry if: No improvement despite repositioning and tummy time. If head shape is significantly asymmetric, this is the optimal window for helmet therapy if needed.

8-18 months

Normal: Head shape continues to round out as skull grows. Most positional flattening resolves significantly by 2 years.

Worry if: Severe plagiocephaly that has not improved. After 12-14 months, helmet therapy is less effective as skull growth slows.

Home Care

  • Supervised tummy time starting from birth — aim for 30-60 minutes total per day by 3 months
  • Alternate which direction baby's head faces during sleep (alternating ends of crib)
  • Alternate which arm you hold baby in during feedings
  • Limit time in car seats, bouncers, and swings when not in the car
  • Encourage baby to look to the less-preferred side using toys and voices
  • Hold baby upright when awake to reduce pressure on the back of the head
  • If torticollis is present, gentle stretching exercises as directed by a physical therapist
  • Continue placing baby on back for sleep — do NOT use positioning devices

Frequently asked questions

What causes flat head (plagiocephaly)?
Positional preference (always sleeping in same direction) (common); Back sleeping position (safe but can cause flattening) (common); Torticollis (tight neck muscle limiting head rotation) (common); Premature birth (softer skull bones) (uncommon); Multiple birth (limited space in utero) (uncommon); Craniosynostosis (premature fusion of skull sutures) (rare)
When is this an emergency?
Head shape abnormality noted at birth with visible ridge along suture (possible craniosynostosis). Rapidly changing head shape with signs of increased intracranial pressure (bulging fontanelle, vomiting)
What can I do at home?
Supervised tummy time starting from birth — aim for 30-60 minutes total per day by 3 months. Alternate which direction baby's head faces during sleep (alternating ends of crib). Alternate which arm you hold baby in during feedings. Limit time in car seats, bouncers, and swings when not in the car. Encourage baby to look to the less-preferred side using toys and voices. Hold baby upright when awake to reduce pressure on the back of the head. If torticollis is present, gentle stretching exercises as directed by a physical therapist. Continue placing baby on back for sleep — do NOT use positioning devices
When should I call the doctor?
Moderate flattening that is worsening despite repositioning efforts. Concern about possible craniosynostosis (ridge felt along skull)

Sources

AAPAAPNHS

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources

Related Symptoms

head bangingbulging fontanelle

Bottom line

Most cases of flat head (plagiocephaly) in babies are not emergencies. However, seek immediate care if head shape abnormality noted at birth with visible ridge along suture (possible craniosynostosis).

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.