Cranial shape during early neonatal period in Japanese newborns: Observational study.

This study aimed to investigate whether cranial shape measurements obtained immediately after birth can be used to determine the timeline and mechanisms underlying the development and progression of cranial deformities in healthy infants. This study examined the cranial geometry of normal newborns immediately after birth at Nihon University Itabashi Hospital and Kasukabe Medical Center. Measurements were obtained using stereophotogrammetry and 3-dimensional cranial data were analyzed using image analysis software. According to international criteria, positional deformational plagiocephaly (PDP) was identified at a cranial vault asymmetry index >3.5%, whereas positional brachycephaly was identified at a cephalic index ≥81%. These data were compared with those from a previously reported database of 1-month-old infants. A total of 130 newborns with a mean gestational age of 39 weeks, a mean birth weight of 3075 g, a mean head circumference of 33.5 cm, and a male sex ratio of 48.5% were included. The mean age at measurement was 3.3 days. The prevalence of PDP and positional brachycephaly was 19.2% and 86.2%, respectively. No notable differences in the background characteristics were observed between the PDP and non-PDP groups. The mean cephalic index was significantly lower in breech fetuses (P = .015), with no significant differences between the delivery methods. The symmetry-related parameters of cranial deformities were more pronounced at 1 month than at birth, with a substantially higher median cranial vault asymmetry index of 4.9% and 2.1%, respectively (P < .01). The prevalence of PDP increased significantly from 19.2% at birth to 66.1% at 1 month of age. Our findings suggest that cranial deformities become more pronounced within the first month after birth. Prevention at an early stage will be the focus of future research.