Fertility and infertility: Definition and epidemiology

Mélodie Vander Borght, Vander Borght M, Christine Wyns, Wyns C
Clinical biochemistry · 2018 · vol. 62 , pp. 2–10 · doi:10.1016/j.clinbiochem.2018.03.012 · PMID:29555319 · W2790887288
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⚙ AI-generated summary by gemini-2.5-flash-lite+body, 2026-06-12 ⓘ

This paper defines infertility as the failure to achieve pregnancy after 12 months of intercourse and discusses its epidemiology, prevalence, contributing factors, and age-related decline in both genders.

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The paper defines infertility as the failure to achieve clinical pregnancy after 12 months of regular unprotected intercourse and estimates that it affects 8–12% of reproductive-aged couples worldwide, with male factors accounting for 20–30% of cases but contributing to 50% overall. It reviews epidemiologic influences on spontaneous conception, including the duration of non-conception, female partner age (with fertility decline beginning around 25–30 years), and disease-related infertility, and it lists major causes affecting each gender. For females, it highlights that secondary infertility is the most common and notes potential roles for reproductive tract infections and conditions such as endometriosis, uterine fibroids, and endometrial polyps, while also covering male causes such as testicular and post-testicular deficiencies. As a narrative epidemiologic overview, the paper does not present new original data and provides caveats typical of synthesizing heterogeneous estimates across populations. Relevance to endometriosis: endometriosis is explicitly cited as a potential contributor to female infertility within a broader epidemiologic discussion, though the paper’s main focus is the definition and epidemiology of fertility and infertility.

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Abstract

Infertility is a disease characterized by the failure to establish a clinical pregnancy after 12 months of regular and unprotected sexual intercourse. It is estimated to affect between 8 and 12% of reproductive-aged couples worldwide. Males are found to be solely responsible for 20-30% of infertility cases but contribute to 50% of cases overall. Secondary infertility is the most common form of female infertility around the globe, often due to reproductive tract infections. The three major factors influencing the spontaneous probability of conception are the time of unwanted non-conception, the age of the female partner and the disease-related infertility. The chance of becoming spontaneously pregnant declines with the duration before conception. The fertility decline in female already starts around 25-30 years of age and the median age at last birth is 40-41 years in most studied populations experiencing natural fertility. The disease-related infertility may affect both genders or be specific to one gender. The factors affecting both genders' fertility are hypogonadotrophic hypogonadism, hyperprolactinemia, disorders of ciliary function, cystic fibrosis, infections, systemic diseases and lifestyle related factors/diseases. Premature ovarian insufficiency, polycystic ovary syndrome, endometriosis, uterine fibroids and endometrial polyps may play a role in female infertility. Male infertility may be due to testicular and post-testicular deficiencies. Semen decline that has been observed over the years, endocrine disrupting chemicals and consanguinity are other factors that may be involved.
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Fertility and infertility: Definition and epidemiology. (2018) Clinical Biochemistry — Vol. 32, p. 2-10 (2018) (2018) Clinical Biochemistry — Vol. 32, p. 2-10 (2018) Open Access - Adobe PDF - 884.75 KB - Authors - Author Vander Borght, Mélodie UCLouvain - Author Wyns, Christine UCLouvain - Abstract - Infertility is a disease characterized by the failure to establish a clinical pregnancy after 12 months of regular and unprotected sexual intercourse. It is estimated to affect between 8 and 12% of reproductive-aged couples worldwide. Males are found to be solely responsible for 20-30% of infertility cases but contribute to 50% of cases overall. Secondary infertility is the most common form of female infertility around the globe, often due to reproductive tract infections. The three major factors influencing the spontaneous probability of conception are the time of unwanted non-conception, the age of the female partner and the disease-related infertility. The chance of becoming spontaneously pregnant declines with the duration before conception. The fertility decline in female already starts around 25-30 years of age and the median age at last birth is 40-41 years in most studied populations experiencing natural fertility. The disease-related infertility may affect both genders or be specific to one gender. The factors affecting both genders' fertility are hypogonadotrophic hypogonadism, hyperprolactinemia, disorders of ciliary function, cystic fibrosis, infections, systemic diseases and lifestyle related factors/diseases. Premature ovarian insufficiency, polycystic ovary syndrome, endometriosis, uterine fibroids and endometrial polyps may play a role in female infertility. Male infertility may be due to testicular and post-testicular deficiencies. Semen decline that has been observed over the years, endocrine disrupting chemicals and consanguinity are other factors that may be involved. - Affiliations - APA - Chicago - FWB Vander Borght, M., & Wyns, C. (2018). Fertility and infertility: Definition and epidemiology. Clinical Biochemistry, 32, 2-10. https://doi.org/10.1016/j.clinbiochem.2018.03.012 (Original work published 2018)

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Condition tags

infertility

MeSH descriptors

Evidence-Based Medicine Fertility Global Health Infertility, Female Infertility, Male Animals Female Fertility Humans Incidence Infertility, Female Infertility, Female Infertility, Female Infertility, Female Infertility, Male Infertility, Male Infertility, Male Infertility, Male Male Prevalence

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