ABSTRACT
The terms infertility, sterility and infecundity are often used loosely, without regard to precise definition. Moreover, definitions of the terms may differ substantially between demographic and medical usage, and between languages.1 In English demographic terminology, primary infertility (also called primary sterility) is defined as the inability to bear any children, due to either the inability to conceive or the inability to carry a pregnancy to a live birth. In medical studies, however, infertility is usually defined as the inability to conceive. In English demographic language, the term infecundity refers to the inability to conceive after several years of exposure to the risk of pregnancy. Inability to conceive within 2 years of exposure to the risk of pregnancy is the epidemiological definition recommended by the World Health Organization.2,3 Clinical studies often use a 1 year period of exposure. In demographic studies it is common to use a period of 5 years of exposure. Accepted categories of infertility include male factor,
tubal disease, anovulation, endometriosis and unexplained infertility.4 In unexplained infertility as the name implies, the mechanism(s) resulting in infertility are unknown. Occult problems in either the sperm or the oocyte leading to fertilisation failure or dysfunctional embryos may be the underlying mechanism of unexplained infertility. Alternatively at the level of the endometrium implantation failure, in spite of availability or replacement of morphologically good quality embryos in assisted reproductive technology (ART), may be the mechanism of unexplained infertility.
