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.