Recently, a plethora of growth standards are being suggested for the identification of small for gestational age (SGA) fetuses. Given their intrinsic differences in design, method of acquisition, and the characteristics of the populations, their generalizability for other populations is questionable. This study aimed to assess the differences in SGA and severe SGA rates using five different growth standards. A retrospective cohort study of all singleton deliveries, was conducted in two campuses of tertiary referral hospitals with more than 10,000 births annually, between January 2019 and July 2022. SGA and severe SGA was defined as birthweight below the 10th or 3rd percentile, respectively, for each growth standard. The SGA and severe SGA rate were compared between the following growth standards: Hadlock, Fetal Medicine Foundation (FMF), World Health Organization (WHO), INTERGROWTH-21 (IG-21), and local population-based growth standard. The study population included 38,715 singleton deliveries. The SGA and severe SGA rate significantly differed among the growth standards (Figure1, Figure2). Of note that 8,928 (23.06%) and 4,676 (12.08%) fetuses were considered SGA and severe SGA, respectively, according to the Fetal Medicine Foundation growth chart, while only 2,347 (6.06%) and 128 (0.33%) considered SGA and severe SGA, respectively, according to the local population-based growth charts (P< 0.001). Our study demonstrates a significant variety of SGA and severe SGA rates using different growth standards. Therefore, the decision on the growth standards in use is critical given the significant influence on clinical management.View Large Image Figure ViewerDownload Hi-res image Download (PPT)