To investigate the epidemiological characteristics and identify associated factors of cranial deformities among infants in the Yan′an region of northwestern China.

This retrospective study analyzed the clinical data of 1 406 infants undergoing cranial measurements at the Yan′an Branch of Peking University Third Hospital between September 2024 and August 2025. Participants were stratified by age into 3 groups (0-4, 5-8, and 9-12 months), and based on the measurement results, cranial deformities were classified into mild, moderate, and severe categories. Chi-square tests with Bonferroni correction evaluated differences in incidence rates and etiologies across groups. The Cochran-Armitage test analyzed linear trends with age, and the Kruskal-Wallis H test compared the overall distribution of deformity severity.

Among the 1 406 infants, 554 were aged 0-4 months, 470 were aged 5-8 months, and 382 were aged 9-12 months, of whom 812 presented with cranial deformities (345, 265, and 202 cases across the respective groups). The overall incidences of isolated plagiocephaly, isolated brachycephaly, combined plagiocephaly and brachycephaly, and scaphocephaly were 14.9% (210/1 406), 18.6% (262/1 406), 21.9% (309/1 406), and 2.2% (31/1406), respectively. The detection rate of isolated brachycephaly differed significantly among groups (χ²=10.070, P< 0.01) and showed a decreasing trend with increasing age (trend test: χ²=10.066, P<0.01). No significant differences were observed for plagiocephaly and scaphocephaly (χ²=1.707, 0.084, all P> 0.05). Among infants with cranial deformities, the 0-4 month group had significantly higher rates of prematurity [11.9%(41/345)], adverse perinatal factors [20.9%(72/345)], and congenital muscular torticollis [5.5%(19/345)] compared to the 5-8 month [5.3%(14/265), 6.4%(17/265), 0.4%(1/265)] and 9-12 month [6.4%(13/202), 9.4%(19/202), 0.5%(1/202)] groups. Conversely, the rate of fixed supine sleeping positioning was the lowest in the 0-4 month group [80.0%(276/345), 89.8%(238/265), 90.1%(182/202)] (χ²=9.828, 30.692, 20.323, 16.004, all P<0.01).

Combined plagiocephaly and brachycephaly is the most common infant cranial deformity, while isolated brachycephaly incidence shows a decreasing trend with increasing age. Prematurity, adverse perinatal factors, and congenital muscular torticollis are associated factors for early-onset (<4 months) deformities, highlighting the critical need for early screening and targeted interventions.