Of all the gear you collected for your new baby, a helmet probably wasn’t on your list—and yet, more and more American parents are wondering whether a helmet will fix their babies’ plagiocephaly, colloquially known as flat-head syndrome. The skull deformity, which develops in one-third to one-half of all babies born in the United States, is an unintended consequence of the Safe to Sleep campaign to help prevent Sudden Infant Death Syndrome (SIDS), the leading cause of death among infants between one month and one year of age. Launched in 1994, the campaign worked: In teaching parents to put their babies to sleep on their backs instead of on their tummies to reduce risk of suffocation, the initiative has cut SIDS cases by more than half since its launch.

The downside is that prolonged pressure on the backs and sides of babies’ soft skulls means more instances of deformity. “No doubt, plagiocephaly has greatly increased since the campaign started,” says Children’s Hospital Colorado neurosurgeon Dr. Corbett Wilkinson, who estimates the national rate has at least doubled since the early 1990s.

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Treatments include physical therapy, positional changes, and infant helmets—but which is best? Children’s is working on an answer. To improve diagnosis and treatment without the use of infant helmets (which can run about $1,800), researchers are conducting an ongoing study of 300 Denver-area babies with plagiocephaly. Using the only 3-D cranial-scan technology in Colorado, the study amasses images of children with craniofacial differences. The 360-degree camera measures the skull down to the millimeter. As children return regularly after intervention begins, the aggregated data will ultimately help build a head-measuring app to assist pediatricians in determining if a case is mild, moderate, or severe.

Meanwhile, Children’s doctors suggest physical therapy and an “active counterpositioning” approach—placing the baby in her crib or chair in a way that relieves pressure on the flat part of the head—for mild to moderate cases. (See “Plagio Prevention.”) “We recommend helmeting only rarely, for deformational plagiocephaly that is either relatively severe or associated with a condition that limits ability to undertake [positional] therapy,” says Dr. Brooke French, co-director of the congenital craniofacial surgery program at Children’s.

Contrary to many new parents’ fears, plagiocephaly doesn’t cause developmental delays, though if left untreated, it can lead to psychosocial problems for the child and her parents. “If there’s a flattening that’s noticeable to everyone,” Wilkinson says, “you need to come see the doctor.”