After squeezing through the birth canal, it's no wonder that many a newborn emerges looking like a Saturday Night Live conehead. An infant's skull is designed to change shape, with plates of bone that compress during delivery and expand to accommodate brain growth. This malleability, however, can also lead to a lopsided head, a problem that is no laughing matter.

The condition, called positional plagiocephaly, occurs when a child rests his head on the same side for long periods of time, causing a flat spot. It is now diagnosed in 2 percent of infants, a five- to sixfold increase since 1974. Contrib-uting to this rise is the fact that more parents now place their babies to sleep on their backs, a position proven to reduce the risk of sudden infant death syndrome (SIDS). Parents worried about their baby's head shape, however, should not give up on back sleeping, says John Kattwinkel, M.D., a neonatologist at the University of Virginia in Charlottesville. Instead, they should change their baby's position when he's awake and observed, by placing him on his stomach for tummy time and limiting the time he spends reclining in a carrier.

If parents notice a flat spot developing, they should seek their pediatrician's advice as soon as possible, says John Graham, M.D., director of clinical genetics and dysmorphology at Cedars Sinai Medical Center in Los Angeles. While a lopsided head won't harm a baby's brain, positional plagiocephaly may lead to more noticeable facial deformities if it's ignored. It is usually treated with an orthotic band or helmet.

A flat spot may also be the result of a health problem such as torticollis (literally, twisted neck), which occurs when shortened neck muscles on one side keep a baby's head fixed in one position. Signs include difficulty nursing equally on both breasts (though many babies have a favorite side) or if the baby is uncomfortable turning his head. Torticollis can be corrected with physical therapy.

A rarer, more serious head shape disorder is craniosynostosis, which occurs when the skull bones prematurely fuse together before birth. A specialist diagnoses it by a physical exam, an X ray, or a CT scan. Treatment for craniosynostosis requires surgery, which a baby may undergo as early as three months of age. For more information, visit www.cappskids.org, www.plagiocephaly.org, or www.torticolliskids.org. For a physician referral, contact the Cleft Palate Foundation at 800/242-5338.

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