Ultrasound reference value of frontal-occipital horn ratio for neonates born at 25–41 gestational weeks

This study aimed to establish a reference range for frontal-occipital horn ratio (FOHR) in neonates and identify factors associated with FOHR variation. This prospective research enrolled neurologically normal neonates born at or admitted to two Chinese Grade 3A Hospitals between July 2022 and November 2023. Spearman's rank correlation and median regression with bootstrap standard errors were utilized to assess factors associated with FOHR. Intraclass correlation coefficients (ICC) were calculated to evaluate the measurement reliability of FOHR. A total of 1,579 neurologically normal neonates were included. The FOHR showed no significant association with any of the variables examined in the adjusted median regression analysis. Its central 90% reference interval (P5–P95) ranged from 0.37 to 0.46, and the potential surgical threshold is 0.55, requiring clinical validation. The intra- and inter-rater ICCs indicated moderate-to-good reliability for FOHR measurement. We present the reference value of FOHR for neonates and compare its upper limits across all available studies. The FOHR showed no significant association with any of the factors examined in the study, and its measurement reliability is clinically acceptable.