Uncorrected Proof J Compr Ped. In Press(In Press):e108667. Published online 2021 August 8. doi: 10.5812/compreped.108667. Research Article Exclusive Breast Feeding and Its Determinants in Infants Born in Zanjan Hospitals: A Longitudinal Study Fariba Hadi 1 , Hasan Eftkhar 2 , Abolghassem Djazayery 3 and Saeideh Mazloomzadeh 4, * 1 Department of Health, Zanjan University of Medical Sciences, Zanjan, Iran 2 Department of Health Education and Promotion, School of Public Health and Institute of Public Health Researches, Tehran University of Medical Sciences, Tehran, Iran 3 Department of Nutrition and Biochemistry, Tehran University of Medical Sciences, Tehran, Iran 4 Department of Epidemiology and Statistics, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran * Corresponding author: Department of Epidemiology and Statistics, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran. Email: smazloomzadeh@zums.ac.ir Received 2020 October 02; Revised 2021 June 17; Accepted 2021 July 06. Abstract Background: Exclusive breastfeeding (EBF), especially during the first six months of life, is one of the primary health indicators in infants. Objectives: The present study intended to describe the frequency of EBF in infants and its determinants until six months after birth. Methods: This longitudinal study was conducted on 673 mother-newborn pairs visiting obstetrics and gynecology departments of two main hospitals in Zanjan. Information on the frequency of EBF up to six months, socio-demographic and reproductive infor- mation, and attitudes of mothers towards breastfeeding was gathered using questionnaires. Data were analyzed using chi-square test and logistic regression in SPSS. Results: The proportion of neonates who were receiving EBF at discharge was 95.7%. The EBF proportions in the second week, the first, fourth, and sixth months were 95%, 88.1%, 80.7%, and 77.3%, respectively. The multivariate analysis of data indicated that living in urban areas (P = 0.02), lower education of mothers (P = 0.008), having more than three years of birth interval (P = 0.006), no experience of breastfeeding in mothers (P = 0.01), no prior decision for breastfeeding in mothers (P < 0.0001), and use of artificial nipples (P = < 0.0001) were independently associated with non-EBF. Conclusions: In this study, despite a high proportion of EBF at discharge, we found that the proportion of EBF reduced during six months. The determinants of non-EBF at six months, including urban and less educated mothers, highlight a need to promote awareness regarding EBF and perform interventions for women at a greater risk for early breastfeeding cessation. Keywords: Breastfeeding, Newborns, Iran 1. Background The benefits of breastfeeding for neonates and in- fants are well-documented (1). Several medical societies have recommended exclusive breastfeeding (EBF) during the first six months after birth (2-5). The World Health Organization (WHO) recommended EBF during the first six months after birth and continued breastfeeding for children up to two years old and even after. The single most cost-effective intervention to reduce infant mortal- ity in the developing countries is the promotion of EBF (6-9). Sub-optimal breastfeeding (especially non-exclusive breastfeeding throughout the first six months after birth) is estimated to result in 1.4 million deaths and 10% of all diseases in children under five years old. The long-term im- pacts of non-exclusive breastfeeding include reduced pro- ductivity, poor school performance, and impaired intel- lectual and social development. Non-exclusive breastfeed- ing could also increase the risk of death due to diarrhea and pneumonia among infants under five months by more than twofold (7). The World Health Organization recom- mends EBF as a strategy to reduce infant mortality (10). Several causative factors lead to infant mortality. Under-nutrition is an underlying cause of two-fifths (2/5) of all child deaths (11). Previous studies have established the benefits of breastfeeding for both children and their moth- ers (12). Exclusive breastfeeding has been related to sig- nificant reductions in adverse health outcomes, including gastrointestinal and respiratory infections (13). Early and adequate breastfeeding is effective in preventing neonatal jaundice. Inadequate breastfeeding was reported as one of the major causes of neonatal jaundice (14). Exclusive breastfeeding is a substantial supply of nu- Copyright © 2021, Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.