Flat, uneven or rounded: Why babies' head shapes vary

Many newborns have slightly lopsided heads. Sometimes, it's because their heads get molded unevenly in the tight space of the birth canal during birth.

Fortunately, babies' skulls are designed to withstand such pressure. The bones of the skull don't fuse until your baby is 15 to 18 months old. Unfused skull bones give your baby's head the flexibility it needs for birth. The soft spots (fontanels) between the unfused skull bones also give the brain room to grow. In fact, your baby's brain will double in size in the first year and a half after birth.

How position affects head shape

Skull flexibility is one of the biological advantages nature has given babies to help them survive and develop. But because your baby's skull is malleable, too much time in one position can give it an uneven shape well past the time when uterine or birth-related head malformation should have resolved. This later head malformation, known as positional molding, develops in babies who spend most of their time on their backs in cribs, car seats or infant seats. Positional molding may reinforce a birth-related head malformation, or it may create flattening or elongation in a baby whose head was evenly shaped at birth.

Positional molding is most noticeable when you're looking down at the back of your baby's head. From that angle, the back of the head looks flatter on one side than on the other, and the cheekbone on the flat side protrudes. The ear on the flat side also may appear to be pushed forward.

Irregular head shape caused by excessive back-lying is increasingly common because parents are following pediatricians' advice and placing babies faceup during sleep. In the years since "back to sleep" became the byword, rates of sudden infant death syndrome (SIDS) have fallen dramatically. A higher rate of positional molding, which is temporary and easy to correct, is clearly a low price to pay for such an important benefit.

How to straighten things out

•  Vary the position of your baby's head, turning it to the right or left, when he or she is in a car seat, infant carrier, or crib.

•  Place your baby on his or her stomach to play with you. Be sure to focus your attention on your baby during these tummy-down sessions. Never put your baby face-down and then leave the room.

•  Place a foam wedge or a towel, rolled lengthwise, along your baby's back to prop him or her onto one side to sleep.

•  Alternately lay your baby down with his or her head toward the foot rather than the head of the crib. Also, try alternating the direction your baby faces — left or right — during sleep.

•  Position your baby so that he or she will have to turn away from the flattened side of the head to look at you or to track movement or sound in the room.

Varying your baby's head position usually evens out the sides of the head. If the malformation persists after two or three months, your baby's doctor might prescribe a special headband or molded helmet to help shape the head. These devices generally start to restore head symmetry within a few days of continuous wear. Babies usually wear them for less than a year.

A more serious cause

In very rare circumstances, two or more of the bone plates in a baby's head fuse prematurely, causing inflexibility. This rigidity pushes other portions of the head out of shape as the brain expands. Doctors aren't sure what causes this condition, known as craniosynostosis (kra-ne-o-sin-os-TO-sis). The treatment for this condition is surgical and is usually successful if done before fontanel closure.

Keep it in perspective

If you spend lots of time worrying about the shape of your baby's head, you'll miss some of the fun of being a new parent. In a few short months, your baby will have much greater control of the head and neck muscles, and his or her voluntary movements will keep pressure more evenly distributed on the skull. The head is just one example of the dramatic growth and development that your baby experiences during the first year of life. Although occasional worries are unavoidable, chances are your baby is right on track.