Background and purpose: Reducing the desire to have children is one of the most important concerns and challenges in developed and developing countries. Also, the current policies in these countries try to understand the factors related to it, and until today, through this way, it has led to an increase in the population in countries with an aging population. Considering the importance of this issue, we decided to prepare and compile a study to determine the factors related to the desire to have children systematically. Materials and methods: This study was conducted in 2024, which is a systematic review, and was conducted in five stages, which included designing the study question, searching, extracting related studies, selecting related studies, tabulating information, and reporting the results. Was. Searching in domestic and foreign databases including SID, PubMed, magician, Iran doc, Science Direct, Scopus, and Google Scholar search engine with keywords such as "related factors", "childbearing", "psychological factors", "social factors", Cultural factors, "physical factors", "individual factors", "religious factors", "decrease", "Iran" and "tendency" and their English equivalents were carried out. Studies were reviewed in the period from 2012 to 2024 (the last twelve years, due to major changes in the world). To select studies, inclusion or exclusion criteria were considered. Also, the quality screening of the studies was done by the Newcastle checklist. After selecting and checking the quality, the data in the studies were classified. Results: Based on the answer to the main research question, the findings were classified into three categories: social and environmental factors, psycho-physical factors, and demographic factors. The review of 16 cross-sectional studies showed that factors such as sex, age, marriage, education, race, and place of residence are included in the demographic class. Among other relevant factors is the desire to have children. Religion and religion, technological progress, life experiences, culture and politics governing the society, family structure, peers and economic issues, and access to the media are among other related issues that are included in the category of social and environmental factors and are mentioned in 6 studies. became. The analysis of 7 other cross-sectional studies pointed to the connection of the next class, i.e. psycho-physical factors. In these studies, factors such as personality, depression, self-esteem, underlying disease, and fertility and infertility records were related to having children. It should be noted that some studies were placed in several classes and the classes overlapped. Conclusion: Based on the findings of this study, it can be concluded that there are many factors related to people's desire to have children, which the studies in this research are not sufficient in expressing. But it is possible to take help from these factors that have been mentioned in various studies as a guide to know the related factors and by planning to manage or strengthen some of them, help to increase the desire to have children.