Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 50 2 2021 02 01 369 375 Reyhaneh SEFIDKAR Department of Biostatistics, School of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Farid ZAYERI 1. Department of Biostatistics, School of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2. Proteomics Research Center and Department of Biostatistics, School of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Elaheh KAZEMI Department of Biostatistics, School of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Masoud SALEHI Department of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran Afsaneh DEHNAD Department of Foreign Languages, School of Management and Informatics Health, Iran University of Medical Sciences, Tehran, Iran Maryam HAFIZI Department of Foreign Languages, Shiraz Branch, Islamic Azad University, Shiraz, Iran 2019 03 01 2019 05 22 Background: Preterm birth is the most important in children under 5 yr mortality. In this study, we used the Global Burden of Disease Data (GBD) to evaluate the trend of preterm infant mortality rate for all countries from 1990 to 2017 and to assess the effect of development factors on this trend. Methods: The preterm infant mortality rate data from 196 countries of the world, from 1990 to 2017, were extracted from the GBD database. To study the trend of preterm infant mortality rate, a mixed-effects log-linear regression model was fitted separately for each IHME super-region. In the next step of data analysis, the development factor was included in the model to determine its effect on this trend for all countries under study. Results: The average rate mortality rate has declined about 2% per year throughout the world over the mentioned period. The highest and lowest decreasing trends were observed in high-income countries (about 4.0%) and Sub-Saharan Africa (about 1.0%), respectively. Including the effect of development factor in the mentioned model revealed that in 1990, the rate of preterm infant mortality in developed countries was 2.2 times of this rate in developing countries and this rate ratio has increased to 2.69 in year 2017. Conclusion: Although the preterm infant mortality rate were decreasing in all super regions, there is a remarkable gap in this rate between developing and developed countries yet. Therefore, preventative strategies are needed to reduce preterm birth and its burden, especially in the developing world. https://ijph.tums.ac.ir/index.php/ijph/article/view/16391 https://ijph.tums.ac.ir/index.php/ijph/article/download/16391/7137