Infertility affects around one in seven couples of reproductive age. The main causes of infertility are female factor (anovulation, tubal damage, endometriosis and ovarian failure), male factor (low or absent numbers of motile sperm in the ejaculate, and erectile dysfunction), or unexplained infertility. A woman of reproductive age who has not conceived after a year of regular sexual intercourse, and has no known cause of infertility, should be offered referral for further clinical assessment and investigation with her partner. [With external links to the current evidence base]