Infertility is defined as the inability to spontaneously conceive with regular intercourse over a period of at least 1 year. Prevalence of overall couples with infertility is 15%.

Primary infertility is when a woman has never been pregnant (nulliparous). Prevalence of primary infertility increases with age: women aged 15-34 years (7.3%-9%), aged 35-39 years (25%), and aged 40-44 years (30%).

Secondary infertility occurs when a woman has previously been pregnant and delivered a baby but is now experiencing infertility.

Causes of infertility can be broken down into factors based on population data. These factors are present in both primary and secondary infertility:

• Male factor (hypogonadism, post-testicular defects, seminiferous tubule dysfunction) – 26%-50%
• Ovulatory dysfunction (anovulation, polycystic ovarian syndrome [PCOS]) – 21%
• Tubal damage (pelvic inflammatory disease) – 14%
• Endometriosis (scar tissue affecting the fallopian tubes) – 6%
• Coital problems (psychological, marital discord) – 6%
• Cervical factor (cervical stenosis) – 3%
• Unexplained – 28%-30%
• Other causes may include primary ovarian insufficiency, hyperprolactinemia, extremes of weight, and endocrine disorders such as type 2 diabetes.

There is a potential genetic association to infertility with variants in BRCA1 and BRCA2, among other genes.