Worldwide, there is a trend of increasing age at first conception, declining fertility rates and increasing prevalence of unwanted infertility. This outcome has been found to be related to lack of fertility awareness (FA), reproductive choices and their consequences. FA encompasses a comprehensive understanding of reproduction, fertility, individual and non-individual risk factors, and the social and cultural aspects that influence reproductive family planning. Surprisingly, the lack of accurate fertility knowledge is not limited to a specific socio-demographic group. Both educated and uneducated populations tend to show low levels of fertility knowledge, indicating a widespread information deficit and an urgent need for improved education and awareness initiatives. A systematic review conducted by Pedro et al. (2018) revealed important research gaps and identified a paucity of high-quality studies in many countries. In particular, studies have predominantly focused on assessing women's fertility knowledge, revealing a significant gender gap in misinformation and understanding. However, we do not know if this information gap has narrowed in the last five years and which populations are still left out. This review aims to 1) provide an overview of the available research on FK worldwide, building on the research of Pedro et al. (2018), and 2) identify gaps in the literature to inspire new research in FK. Research from January 2017 to February 2023 was conducted through the databases Web of Science, and PubMed, looking for research that evaluated FK as a whole and studies that used quantitative data evaluating different aspects of FK. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to analyze and report their findings. Meeting the PRISMA guidelines provides scientific quality to our research. The investigation led to the inclusion of 55 studies in our collection. Asia accounted for the majority of the research (36.36%), followed by Europe (25.45%) and North America (25.45%). Women from the general public, students, healthcare professionals, and infertile/sub-fertile women made up the majority of the sample. Of the included studies, most assessed FK as a whole with a specific and known questionnaire. The rest explored aspects of FK through their own questionnaires that assessed knowledge of different aspects of FK. The results show that there is still a lack of fertility awareness research worldwide, especially in Africa. Europe and North America have been more active in fertility awareness research, but some European countries, such as Bulgaria, the Czech Republic and others, have limited research in this field. Similarly, there are knowledge gaps in countries such as Portugal, Poland and Switzerland regarding FK among healthcare professionals. Regarding specific populations, female and students have received more attention from researchers, but studies on students in Switzerland are lacking. Some countries, such as Austria, Finland and France, have only focused on students and have knowledge gaps regarding FK in other populations. Denmark, Spain and Germany have not investigated FK in men or couples. In Asia, research on FK in adult populations, couples, and men in countries such as China, Israel, Saudi Arabia, and others is limited. FK in healthcare professionals has not been studied in Thailand, Iran, Japan, Turkey, Pakistan, and Saudi Arabia. Many countries in Asia and Latin America have not been included in the research at all, highlighting the need for further studies in these regions. In conclusion, although there has been an increase in fertility knowledge research in the last five years, general knowledge about fertility does not appear to have improved substantially during this period. Also, although a lot of studies focus on fertility knowledge and many use standardised methodologies, several underrepresented regions and populations remain.