Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 10 4 2025 04 23 421 433 Fatemeh Atarodi Department of Biostatistics, Faculty of Health, Mazandaran University of Medical Sciences, Sari, Iran. Nouraddin Mousavinasab Department of Biostatistics, Faculty of Health, Mazandaran University of Medical Sciences, Sari, Iran Daniel Zamanfar Department of Pediatrics, School of Medicine Diabetes Research Center Sari Bu Ali Sina Hospital, Mazandaran University of Medical Sciences, Sari, Iran Ramezan Fallah Department of Epidemiology and Biostatistics, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Simin Moadikhah 5- Faculty of Medicine, Innovative Medical Research Center, Mashhad Medical Science, Islamic Azad University, Mashhad, Iran Soheila Moadikhah Mashhad Medical Science, Islamic Azad University, Mashhad, Iran 2024 09 01 2024 12 31  Introduction: According to the significance of children in the culture, economy, and human resources for the country's future, their growth in the first 2 years and its influencing factors are crucial for the country's progress. Objectives: The study evaluates the determinants that impact the growth of children in their first two years of life. Methods: This data was collected based on electronic files from 601 children who visited Health Service Centers in North Khorasan province from April 2020 to April 2023. We used longitudinal models (transmission-random-marginal) and SPSS software version 26. We employed the Akaike information criterion, with a significance level of 0.05.  Results: Based on our research, we found that the recommended growth measurements for weight, length, and head circumference for children under 2 years using the longitudinal method. Children's growth was significantly associated with gender, place of residence, mother's education, type of breastfeeding, intrauterine age, singleton birth, and mother's weight (P<0.05). Boys showed better weight growth compared to girls, but the rate of weight and height growth was similar for both genders. Conclusions: According to the results of this study, adequate training on factors affecting children's growth should be provided to both mothers and health workers, which may reduce the risk of developing disorders.    https://jbe.tums.ac.ir/index.php/jbe/article/view/1496