Discussion
This systematic review and meta-analysis of 27 community-based studies indicated the pooled prevalence of infertility was 12.87%, with primary and secondary infertility prevalence rates were 7.34% and 6.01%, respectively. The pooled infertility prevalence was significantly diffed across regions, survey years, population characteristics, and bias levels.
The pooled infertility prevalence in our study was similar to a global meta-analysis at 12.6% (95% CI 10.7% to 14.6%)49. However, our rates are comparatively lower than an April 2023 report by the World Health Organization (WHO), which indicates that about 17.5% of adults worldwide suffer from infertility. This may be due to the fact that WHO covers almost all countries worldwide and only 17 countries were included in this study, resulting in our rates being inconsistent with them. In contrast, a meta-analysis on global female infertility with a prevalence of 46.25%, reported significantly higher rates as they included 20 hospital-based studies and only 4 community-based studies19. On the other hand, our combined prevalence is higher than in some studies. Boivin et al. estimated the prevalence of infertility at 24 months in 25 surveys, with a median prevalence of 9%50. Possibly because some women with low fertility may become pregnant within 12-24 months. Additionally, the prevalence of infertility decreases significantly as the duration of judgment increases, as reported in a study estimating the prevalence and trends of infertility from 1990 to 2010, which found a primary infertility prevalence of 1.9% but using a five-year exposure time51. In summary, our combined prevalence rates fall between the high and low rates observed in other studies, which may reflect the impact of various factors, including research type, screening criteria, geographic region, and cultural background. Further studies should explore these factors in greater depth to obtain a more accurate assessment of the global prevalence of infertility.
In our study, we compared the prevalence of primary and secondary infertility and found that the former was slightly higher than the latter, which is consistent with the results of some studies25, 52 but contrary to others22, 28. These differences may be related to the wide variation in the prevalence of infertility among different regions and populations, and should be taken into consideration when developing prevention and treatment strategies. Notably, some studies do not report the prevalence of primary and secondary infertility45, 46, 53, whereas our combined values include both types of infertility. Future studies should focus on reporting the prevalence of primary and secondary infertility separately. It is important for understanding and managing these distinct types of infertility.
Our study also found that prevalence varied among people in different regions, with Africa having the highest prevalence and North America having the lowest prevalence. This is consistent with other studies, with Mascarenhas et al. reporting the highest infertility rates in South Asia, Sub-Saharan Africa, North Africa/Middle East, Central/Eastern Europe and Central Asia51. It may be related to the high prevalence of infectious diseases54 and relatively poor human resources for health and medical conditions55, among other factors. Gonorrhea, syphilis, vaginitis, etc., which may affect reproductive organ health and lead to infertility56, 57. The prevalence of infertility is on the rise with the increase of time. In modern society, women are getting married later and having children later, and the postponement of the childbearing age is an important factor in the increase of infertility58. Because one of the consequences of delaying childbirth can lead to impaired fertility, age is the most important factor in determining fertility in both men and women59. In addition, changes in lifestyle60 and an increase in disease61, 62may adversely affect the reproductive system, leading to an increase in the prevalence of infertility. Our study found a difference in prevalence between women older and younger than 35 years old. This may be because, at an even earlier age, the number and quality of oocytes decrease but manifest clinically at around 35 years of age63, 64. Further evidence comes from a study of 2112 pregnant women in the UK, which reported that increasing age for both men and women affected the time taken to conceive65. The study adjusted for confounding factors such as coital frequency, body mass index (BMI), smoking and other lifestyle factors and still found women aged >35 were 2.2 times more likely than women aged ≤25 to take more than 2 years to become pregnant.
Our study compared the prevalence of infertility between cohort or prospective follow-up studies and cross-sectional studies, and found that the former was significantly lower than the latter. According to a cohort study of 2,300 women, the proportion of those with infertility was approximately 12%66, while a cross-sectional study found that the prevalence of infertility was approximately 15.7%41. The reason for this difference is that cross-sectional studies are conducted at a single time point and often only capture transient or known symptoms of infertility. In contrast, cohort studies allow researchers to track individual changes over time, which can better control for time factors and fully consider potential risk factors for infertility. Overall, infertility is a complex issue that requires consideration of multiple factors. Targeted measures are needed for populations in different geographical regions and age groups, such as increased investment in medical resources, improved lifestyle, and reduced environmental pollution, to effectively control the incidence of infertility. Furthermore, more research is needed to further explore the causes and solutions of infertility.