We queried the web version of ICHUSHI Ver.5 and CiNii, for literature published from 2013 to July 2023, a period of growing interest in fertility education. In addition, due to differences in fertility education and knowledge between Japan and other countries, we narrowed the search down to Japanese literature. The search keywords were “high school students,” “fertility,” and “education.” As shown in Figure 1, 162 ICHUSHI entries and 90 CiNii entries were found,

from which duplicate literature was excluded. The selection criteria for the target literature were as follows: 1) literature on fertility or sex education whose subject was high school students, 2) literature on fertility or sex education by school nurse teachers, 3) original papers, research reports, practical reports, or educational materials, which were published in academic journals.

The exclusion criteria were: 1) literature whose subject was not high school students, 2) literature whose main theme or purpose was neither fertility or sex education, and 3) literature that did not provide details in the text. Literature was screened by checking the titles and abstracts of the search results. A secondary search of the list of relevant works yielded one hand-researched work, for a final total of ten target works for analysis (Figure 1).

Using the matrix method, which is a structure and process for systematically reviewing literature, we organized the selected works by author, year of publication, study design, target of study, purpose, research method, and results. After considering the content of the ten works, we established two angles of analysis: from the perspective of evaluating Japanese high school students’ knowledge of fertility, “high school students’ knowledge and awareness of fertility”; and from the perspective of school nurse teachers educating on fertility, “points of improvement for the acquisition of correct fertility information.” The target works are shown in Table 1 as items [8] - [17] .

The distribution of works among the target literature by year published was as follows: one work in 2014, one work in 2015, two works in 2016, one work in 2017, and five works in 2021. Seven works targeted high school students, and two works and one journal were related to school nurse teachers.

As shown in the list of citations, the works cited consisted of eight quantitative studies, one qualitative study (semi-structured interview), and one special report. There were seven works on fertility knowledge and awareness among high school students, two on fertility knowledge and awareness among school nurse teachers, and one on fertility in the school curriculum. High school students were surveyed on their aspirations for marriage/children, pregnancy/childbirth, male & female sexual physiology, and male & female fertility. They were also surveyed via the Cardiff Fertility Knowledge Scale - Japanese Version (hereafter, CFKS-J) on their fertility knowledge, interfertility knowledge, and their assessment of the sex education they had received.

60% - 90% of high school students named school as their source for information on fertility [13] [14] [16] . On female fertility, 50% - 60% of knew that smoking

and drinking affects fertility, and about egg aging. About 70% of students knew that a woman’s ability to get pregnant falls after the age of 30 or 36. [9] [11] [14] [16] . On female reproductive physiology, 40% - 60% of girls and 20% - 30% of boys answered that menstruation continues until a woman’s fifties, while 28.6% of boys answered that menstruation continues until death [8] [10] [16] . A majority comprised of 74.4% of girls answered that woman remains fertile until 40 - 50 years old, while 21.6% of boys answered “until death” [10] . Roughly half of students surveyed responded that a woman can get pregnant any time if she is still menstruating [8] .

On the topic of male reproductive physiology, 10% - 20% of boys answered correctly for the item “sperm creation/lifetime” [13] . 40.5% thought that ejaculation was possible until death, and “until death” was the most common response regarding fertility as well, with the largest group (33.6%) thinking that a man remains fertile until death [10] .

High school students’ rate of correct answers on the CFKS-J survey was 41.9%. About 10% of students were aware of facts such as that physique and contraction of the mumps affect fertility, or that one in ten women are infertile [14] [16] . Students who scored highly named the Internet as their source of information [14] . Following a lecture on preconception care, an improvement was seen in six of eleven items related to the subject. 80% of students reported that they had thought about their studies, future careers, and life plan [17] .

Around 50% - 80% of students answered that they wanted to get married before 30. Among those, around 30% said they wanted to marry before 25 [13] [16] . Around 70% - 80% of students said they wanted to have children in the future. 60% - 80% said they wanted children between the ages of 25 - 30. Among those, 39% wanted to have children by the time they turn 25 [9] [12] [14] [16] [17] . Regarding the specific age at which they hope to have children, boys answered 28.1 years and girls 26.4 years. Students hoped to finish having children between the ages of 30 - 35 [8] [9] [17] .

27.9% of school nurse teachers answered that the age of declining fertility is “40 or older”. 42.1% answered that natural pregnancy is possible until “45 or older”. While 90.5% of school nurse teachers answered that they were able to teach about the establishment of pregnancy (ovulation, fertilization, and so on), only 40% - 50% said the same for the freezing of egg/sperm cells, egg/sperm donation, egg aging, and the causes of infertility [11] . Among school nurse teachers’ fertility education experience were “girls on diets,” “irregular menstruation,” “eating disorders,” and “guidance for sexually promiscuous students” [13] .

90% of school nurse teachers said that it was important to learn about fertility and reproductive medicine in school. About half said that the establishment of pregnancy should be covered in elementary school, and egg aging and the causes of infertility covered in high school [11] . They also hoped to include ovulation frequency, egg/sperm cell longevity, and the significance of menstruation and ejaculation in the curriculum. School nurse teachers employed at high schools cited menstruation, pregnancy, childbirth, sexual victimization, gender dysphoria, and counseling on sexuality for male students as areas of improvement related to sex education [13] .

Caution points mentioned included consideration of students’ stage of development, overlap with other school subjects, connectedness with previously taught material, avoiding causing anxiety, avoiding giving the impression that sex always results in pregnancy, and avoiding giving students negative impressions about sex [12] . Potential tasks for the future “teaching awareness of fertility while having students consider their life design so they can build a happy family” and “the possibility of including fertility in the instruction on menstruation that happens before the students’ class trip [13] .

Due to rapid societal and lifestyle in recent years, new sex-related issues such as problem behaviors and infectious diseases issues have surfaced. Based on these changes and Japan’s low level of fertility awareness, the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) revised its official Courses of Study curriculum guidelines for the first time in ten years in 2017 and 2018 [7] [18] . In addition, the Cabinet Office’s “Measures for a Society with a Low Birthrate” revised the high school curriculum guidelines as part of its objective to “disseminate education on pregnancy and the roles of the household and family” in an effort to enhance the content of education on family/household functions and child-rearing support [19] . We expected this to result in a larger number of target works published in 2021, but there was not much literature on future fertility focused on high school students.

Many high school students named classes at school as their source for fertility information. This indicates that high school age is the best time to provide students with correct fertility information, giving them the opportunity to accept their own sexuality and consider their futures.

In 2020, the Cabinet Office updated its target for the “rate of understanding of correct medical/scientific knowledge on pregnancy and childbirth” from 2015’s 34% to 70%, but that target has yet to be met [20] . However, the publication of fertility education materials did have an effect, demonstrated by the fact that half of high school students understand egg aging and the effects of smoking and drinking on fertility. On the other hand, although the students with the highest CFKS-J scores listed the Internet as a source of information, it cannot be definitively said that they acquired correct knowledge online, as it is difficult to judge the correctness of information on the Internet. Considering that fertility is not determined only by eggs or smoking and drinking habits, there seems to be a lack of knowledge about fertility and infertility.

A considerable number of high school students mistakenly believe that menstruation, ejaculation, and pregnancy are possible “until death”. In order to ensure school-based sex education proceeds smoothly with students’ developmental stages in mind, MEXT has added the following guidelines: “In elementary school, the curriculum shall cover the physical changes of puberty and the budding interest in the opposite sex; in junior high school it shall cover the maturation of reproductive functions and appropriate behavior in response to changes associated with maturation; in high school it shall cover puberty and health, married life and health, and aging and health to promote and maintain health throughout life” [7] [21] . However, it can be assumed that the additional condition “Reproductive functions shall only be related as necessary” [22] has created a situation in which fertility-related functions are rarely touched upon. Additionally, the literature indicated a need for opportunities to learn about the fertility and reproductive functions of both sexes, as education on pregnancy focuses disproportionately on menstruation and there is little coverage of male fertility and reproductive functions.

The majority of high school students hoped to marry and have children by the age of 30, indicating that high school students do not have thoughts of marrying and having children later in life. In the 16^th Basic Survey on Birth Trends (2021), the percentage of never-married persons aged 18 - 34 who intend to get married eventually was 81.4% for men and 84.3% for women, a decrease from the previous survey in 2015 [3] . Additionally, the percentage of unmarried 25 - 29-year-olds in Japan in 2015 had increased to 72.7% for men and 61.3% for women [24] . In light of these findings, it can be speculated that some high school students may not be able to form families at the time they wish due to some factors in the future. On the contrary, many high school students thought that they would marry and have children by the age of 30 and, following a lecture on preconception care, were thinking about their careers and life plans. In other words, the acquisition of correct reproductive and fertility knowledge was shown to be an effective means of future life planning. Saito stated that giving students “an opportunity to think” about themselves and their future may itself lead to a willingness to form a family with an awareness of the transition to adulthood [24] . In other words, aiming for high school students to acquire correct knowledge of fertility in the classroom will provide them with an opportunity to think about their fertility and future by learning about and understanding their own bodies, and will also lead them to rethink their future life plans. In addition, it will raise awareness of the risks of sexual activity and the prevention of sexually transmitted diseases, while at the same time reducing the risk of infertility in the future. To this end, it is desirable to create an environment in which high school students can flexibly respond to various life events and provide opportunities to think about future life events not only at school but also at home, in the community, and in various other settings.

School nurse teachers did not have sufficient knowledge about fertility. Most responded that they could teach about the “establishment of pregnancy,” but only about half of them were able to teach about fertility. On the other hand, respondents felt there was a need for education on fertility, as they answered that “egg aging and factors contributing to infertility” and other aspects of fertility should be taught in high schools. Adachi et al. found that “teachers who felt burdened by the education on fertility had a lower amount of knowledge on fertility than those who did not feel burdened” [25] . In addition, Nakamura et al. found that “although school nurse teachers have many opportunities to provide individual guidance on sex, they are not confident in their ability to handle the subject and are anxious about it. Therefore, training is required to improve school nurse teachers’ own teaching skills” [26] . Furthermore, in its study of teachers who are responsible for “Japanese-style school education in the Reiwa era (2019 to present),” MEXT states the importance of teacher training: “It is even more necessary for teachers to keep learning the latest knowledge and skills as the times are changing rapidly” [27] . In other words, the study indicated that school nurse teachers, as specialists in health education, must acquire knowledge about fertility in order to educate on the subject. However, they have a sense of difficulty in securing time to spend on sex education due to their busy workload, lack of cooperation among teachers, and limited number of class hours [26] . And since consideration of developmental stages, overlap with other subjects, relatedness to previously studied content, and timing of education were identified as educational issues, for effective high school sex education it is essential to create an environment in which school nurses can participate in training, foster a common understanding among teachers, and consider school-wide policies.