A nearly 10-fold increase in the prevalence of plagiocephaly has been noted in Texas, and the cause has not yet been identified, according to a report published online April 4 in Archives of Pediatrics and Adolescent Medicine.
Between 1999 and 2007, the most recent year for which "cleaned" state registry data were available for analysis, the prevalence of plagiocephaly rose from 3.0 cases to 28.8 cases per 10,000 live births. "This was equivalent to an average annual increase of 21.2% per year, which is highly statistically significant," said Shane U. Sheu of the TB/HIV/STD epidemiology branch, Texas Department of State Health Services, Austin, and her associates.
Plagiocephaly is characterized by unilateral flattening of the head in either the frontal or occipital region, and can occur in utero or in infancy.
It is thought in some congenital cases to result from intrauterine constraint of the fetal head, perhaps caused by multiple gestation, prolonged labor with the fetal head positioned low in the pelvis, or oligohydramnios. Acquired plagiocephaly is sometimes attributed to the infant remaining in the same horizontal position for extended periods, and has reportedly increased since 1992, when the American Academy of Pediatrics recommended infants sleep on their backs to reduce the risk of sudden infant death syndrome.
A marked increase in plagiocephaly was noted in the Texas Birth Defects Registry in recent years, with definitive diagnoses of 6,295 cases in 1999-2007. Ms. Sheu and her colleagues investigated factors that might help explain this rise (Arch. Ped. Adolesc. Med. 2011 [doi:10.1001/archpediatrics.2011.42]).
The registry did not distinguish congenital from acquired cases. However, the AAP recommendation "was not likely to explain our observed dramatic increase, because our study period began 7 years after the recommendation was released," they noted.
The researchers found that the prevalence of plagiocephaly increased across all demographic groups, regardless of maternal age, maternal race/ethnicity, infant sex, gestational age, or the presence or absence of multiple fetuses. Moreover, the proportion of cases related to multiple gestation remained stable over time.
The prevalence also increased across all clinical groups studied, regardless of the severity of the deformity; whether the infant had related torticollis or oligohydramnios; or what diagnostic or therapeutic procedures were used. The mean age at diagnosis also remained consistent over time.
Analysis of data on other birth defects of the skull or face during the same period showed that all but one also significantly increased, including deformities described as "depressions in skull"; "other skull deformity"; "craniosynostosis"; "Goldenhar syndrome/hemifacial microsomia"; "hypertelorism, telecanthus, wide-set eyes"; and "other skull or face bone anomalies." Only "asymmetrical head" declined over time, and that decline was not great enough to account for the rise in defects described as "plagiocephaly."
There was a slight increase over time in the proportion of cases born preterm, but "it would not explain the ninefold increase in plagiocephaly," Ms. Sheu and her associates said.
In short, "we were unable to pin down an explanation for the temporal increase," they said.
Although the increase in plagiocephaly was seen across the entire state of Texas, the bulk of that increase occurred in the Dallas/Fort Worth area, where the prevalence rose from 2.6 cases per 10,000 live births in 1999 to 60.5 cases per 10,000 live births in 2007. This trend appears to have been driven by the fact that five of the seven hospitals where most cases were diagnosed are located in the Dallas/Fort Worth region, and six of them have specialized craniofacial clinics.
This finding suggests that the rise in cases of plagiocephaly is related to increased referral to or increased treatment at these centers. It is possible that more parents are now requesting referrals, that more primary care physicians are recommending them, that marketing of assessment or treatment services has increased, or that reimbursement now offers incentives to have infants evaluated or treated.
For example, reimbursable procedures such as the use of orthotic helmets may have been developed or marketed during this time span, prompting increased referrals and diagnoses. Such factors were not within the scope of this study because the birth defects registry doesn’t collect that type of information, the investigators noted.
This study was supported in part by the Centers for Disease Control and Prevention, the Health Resources and Services Administration, and the Texas Department of State Health Services. Ms. Sheu and her associates reported no relevant financial disclosures.