Table 1.

Definitions of infertility found in the literature

Reference	Definition
International Committee for Monitoring Technology and World Health Organization, 2009 Revised Glossary on ART Terminology [15]	Infertility (clinical definition) is a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 or more months of regular unprotected sexual intercourse.
American Society for Reproductive Medicine, 2008 Definitions of infertility and recurrent pregnancy loss [16]	Infertility is a disease, defined by the failure to achieve a successful pregnancy after 12 months or more of regular unprotected intercourse. Earlier evaluation and treatment may be justified based on medical history and physical findings and is warranted after six months for women over age 35 years.
National Institute for Health and Clinical Excellence guideline 2004 [17]	Infertility should be defined as the failure to conceive after regular unprotected sexual intercourse after two years in the absence of a known reproductive pathology.
World Health Organization, 2001 Reproductive Health Indicators for Global Monitoring [9]	Percentage of women of reproductive age (15–49) at risk of pregnancy (not pregnant, sexually active, noncontracepting, and nonlactating) who report trying for a pregnancy for two years or more.
World Health Organization, 1985 Manual for the investigation and diagnosis of the infertile couple [18]	Infertility, primary: The woman has never conceived despite cohabitation, exposure to pregnancy, and the wish to become pregnant for at least 12 months. Infertility, secondary: The woman has previously conceived but is subsequently unable to conceive despite cohabitation, exposure to pregnancy, and the wish to become pregnant for at least 12 months. If the woman has breastfed a previous infant, then exposure to pregnancy should be calculated from the onset of regular menstruation following delivery.
Demographic definition, 1985 The dictionary of demography [19]	The inability to produce a live birth. The term usually refers to women, but men or couples can be the focus of attention. Used without qualification, sterility implies irreversibility, but the term temporary sterility is sometimes used. A distinction is made between primary sterility where a woman has never been able to have a child, and secondary sterility, which occurs after the birth of at least one offspring.
World Health Organization, 1975 The Epidemiology of Infertility – Report of a WHO Scientific Group [8]	Primary infertility: The woman has never conceived despite cohabitation and exposure to pregnancy for at least two years. Secondary infertility: The woman has previously conceived but is subsequently unable to conceive despite cohabitation and exposure to pregnancy for a period of two years; if the woman has breastfed a previous infant, then exposure to pregnancy should be calculated from the end of the period of lactational amenorrhea.