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 the following 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%

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