Many newborns have slightly uneven heads. But is it cause for worry? Understand what causes unevenness in babies' heads and when treatment is needed.

Sometimes a newborn's head is molded unevenly while passing through the birth canal. Babies are born with soft areas on their heads called fontanels. The skull bones in the soft spots haven't yet grown together. The soft spots allow a baby's relatively large head to move through the narrow birth canal. They also accommodate a baby's rapidly growing brain during infancy. A newborn's head that is shaped unevenly right after birth often rounds out over time.

In other cases, a baby's head shape changes after birth. This is a result of pressure on the head when the baby lies in the same position often. Spending too much time lying flat in one position can lead to an uneven head shape well past the time when birth-related lopsidedness evens out. This is known as positional molding or positional plagiocephaly.

Positional molding might be most noticeable when you're looking at your baby's head from above. From that view, the back of your baby's head might look flatter on one side than on the other. The ear on the flat side might look pushed forward.

Your child's health care provider will do a physical exam. If your baby is diagnosed with positional plagiocephaly, changes in the way you position your baby can minimize head unevenness. For example:

• Change your baby's position. Continue to place your baby on the back to sleep. But alternate the direction your baby's head faces in the crib. If your baby moves around while sleeping and settles into the previous starting position, adjust for this next time.
• Hold your baby. Hold your baby upright when awake to help relieve pressure on your baby's head from swings, carriers and infant seats. You might also hold your baby with alternate arms at each feeding.
• Try tummy time. With close supervision and while your baby is awake, frequently place your baby on the tummy to play. Make sure your baby is on a firm surface during tummy time.

Your baby's health care provider also may recommend physical therapy to treat head unevenness. Physical therapy for positional plagiocephaly involves exercises to help change a baby's preferred head position and strengthen the neck and head muscles.

Sometimes an underlying muscular issue — such as torticollis — causes a baby to hold the head tilted to one side. In this case, physical therapy is important to help stretch the affected muscles and allow the baby to change head positions more freely.

Rarely, two or more of the bony plates in a baby's head join too early. This pushes other parts of the head out of shape as the brain grows. This condition is known as craniosynostosis. Craniosynostosis is typically treated during infancy. To give the brain enough space to grow and develop, surgery is needed to separate the fused bones.

If you're concerned about your baby's head shape, talk with your baby's health care provider.