You notice your baby's head looks a little flat on one side, or perhaps at the back. Is it dangerous? Should you worry?
Plagiocephaly — the medical term for an uneven or flat head shape in babies — is very common and in the vast majority of cases completely harmless. But knowing what you can do to prevent and correct it is worthwhile. Here's everything you need to know.
What Is Plagiocephaly?
Plagiocephaly means your baby's head has developed an asymmetrical shape. The most common types are:
- Positional plagiocephaly — the head is flat on one side. The most common type, caused by the baby lying in the same position frequently.
- Positional brachycephaly — the head is flat at the back and wide overall. Caused by the baby spending a lot of time lying on their back.
- Combined — a mix of both.
Positional head flattening is common in infants. The skull is soft and moldable in the first months of life, making it vulnerable to prolonged pressure in one area.
Positional head flattening is not the same as craniosynostosis, which is a rare condition where the skull's sutures (seams) close too early. Craniosynostosis requires medical evaluation and sometimes surgery. Your pediatrician can help distinguish between the two.
How Common Is It?
Studies suggest that up to 30–50% of infants have some degree of head asymmetry in the early months. The vast majority of cases are mild and resolve on their own.
The incidence increased after "safe sleep" guidelines (back-sleeping) were introduced in the 1990s. Back-sleeping is absolutely the most important protection against SIDS, but it does mean babies spend more time with pressure on the back of the head.
Causes of a Flat Head
Positional (most common)
- Spending a lot of time on the back — babies lie on their backs for most of the day and night
- Preference for one side — many babies prefer turning their head to one particular side
- Tight conditions in the womb — especially with multiples or low amniotic fluid
- Torticollis — tight neck muscles that cause the baby to hold their head tilted
Risk Factors
- Premature babies (softer skull)
- Boys (slightly more common than in girls)
- First-time births (tighter conditions in the womb)
- Forceps or vacuum delivery
Signs of Head Flattening
Here's how you can check at home:
- Look from above — hold your baby up and look down at their head. Is it symmetrical, or flat on one side?
- Look from the side — is the back of the head even, or does one side appear flatter?
- Check the ears — are they level with each other, or is one pushed forward?
- The forehead — does one side bulge out slightly more than the other?
Take photos of your baby's head from above at regular intervals. It makes it easier to track changes over time and to document the situation for your pediatrician.
Prevention — What You Can Do from Day One
Tummy Time When Awake
Tummy time is the single most important measure. It relieves pressure on the back of the head and strengthens neck and back muscles.
- Start from day one with short sessions (1–2 minutes)
- Gradually increase to 30–60 minutes per day spread across multiple sessions
- Always be present and supervise
- Place baby on your chest if they protest the floor
Read our guide to tummy time for babies.
Vary Head Position
- During sleep — place your baby with their head alternating to the right and left. Baby should always sleep on their back, but you can vary which direction their head faces.
- When awake — use toys and your voice to encourage baby to turn their head toward the side they rarely use.
- During feeding — alternate arms so baby looks in different directions.
Limit Time in Car Seats and Bouncers
Baby should not spend more time than necessary lying in a car seat, bouncer, or swing. All of these create pressure on the back of the head.
- Use the car seat only in the car
- Alternate between a baby carrier (head is relieved), stroller, and your arms
- Avoid baby sleeping in the bouncer for extended periods
Holding and Carrying
- Hold baby in your arms or a carrier often — this completely relieves pressure on the head
- Try the "football hold" (face-down along your forearm) — strengthens the neck and relieves pressure
- Alternate arms when carrying
Your baby should ALWAYS sleep on their back. This is the most important protection against SIDS (sudden infant death syndrome). Never place your baby on their tummy or side to sleep, even if you want to relieve head pressure. Read our article on safe sleep for babies.
Treatment
Mild Cases (most common)
Most cases resolve on their own with simple measures:
- More tummy time when awake
- Varying head position
- Encouraging the baby to look toward the less-used side
- Holding and carrying
Moderate Cases
If simple measures aren't helping enough, your pediatrician may refer you to a physical therapist. The therapist can:
- Assess whether the baby has torticollis (tight neck muscle)
- Provide specific exercises for the neck and head
- Monitor progress over time
Torticollis — Tight Neck Muscle
Some babies have a tight muscle in the neck that causes them to prefer turning to one side. This is called torticollis and can be treated with:
- Stretching exercises (guided by a physical therapist)
- Encouragement to look toward the restricted side
- Tummy time with toys on the "difficult" side
Torticollis responds best to early treatment. Most babies recover completely with the right care.
Helmet Therapy (Cranial Orthosis)
Helmet therapy is used in a minority of cases — only for significant flattening that doesn't respond to other measures. Your pediatrician or craniofacial specialist will assess whether it's appropriate.
- Typically considered from around 4–6 months of age
- Usually worn for 3–6 months
- The baby wears the helmet 23 hours a day
- Custom-fitted
Research on helmet therapy shows mixed results. Multiple studies have found that mild to moderate positional head flattening resolves on its own over time, with or without a helmet. Most medical guidelines recommend conservative treatment (positioning and tummy time) as the first approach.
Timeline — What to Expect
| Age | What happens |
|---|---|
| 0–2 months | Head flattening can develop. Start tummy time and position variation early |
| 2–4 months | Most cases are noticed now. Best window for prevention and correction |
| 4–6 months | Baby starts rolling and sitting — head shape naturally improves |
| 6–12 months | Head grows rapidly and shape evens out |
| 12–18 months | Most cases are fully or nearly fully resolved |
When to Contact Your Pediatrician
- If you notice clear asymmetry in the head shape
- If baby always prefers turning their head to one side
- If head flattening isn't improving despite 4–6 weeks of consistent efforts
- If you feel a hard ridge or seam along the skull (possible craniosynostosis)
Your pediatrician checks your baby's head at every well-child visit, but it's always fine to bring it up yourself if you're concerned.
Frequently Asked Questions
Is a flat head dangerous for my baby?
No. Positional head flattening is cosmetic and does not affect brain development. The head grows rapidly during the first year, and the vast majority of cases resolve completely or almost completely.
Can my baby sleep with a pillow to prevent flat head?
No. Pillows, wedges, and positioning devices in the crib are dangerous for sleeping babies and are not recommended. They increase the risk of suffocation. Baby should sleep on a flat, firm surface without loose objects.
When is it too late to do something about flat head?
The skull is most moldable in the first 4–6 months. After that it gradually hardens, but the head continues to grow and shape can improve up to about 18 months of age. The earlier you start, the better.
Can too much tummy time be harmful?
No, it's difficult to have too much tummy time as long as your baby is awake and supervised. Most babies signal clearly when they've had enough. Start with short sessions and increase gradually.
Does breastfeeding affect head shape?
It can, indirectly. If you always nurse on the same side, your baby looks in the same direction every time. Alternate sides, or vary your nursing position, to give your baby practice turning their head both ways.
Track Your Baby's Development
Head shape is often linked to motor development. Track your baby's progress with head control, rolling, and tummy time milestones.