Epidemiology of infertility

Epidemiologic studies can define the extent to which infertility is a public health problem by measuring the population prevalence and distribution of infertility, and trends in prevalence over time. Also, epidemiologic investigations can assess the risk of infertility associated with factors such as sexual behavior or contraceptive use, measure the use of infertility care services, and evaluate the efficacy of therapy. This review summarizes important developments in the epidemiology of infertility, but because this is a wide ranging field, special attention is given to recent reviews of interest to clinicians. Infertility generally is defined as the inability to conceive after 1 year of intercourse without use of contraception; childless couples are classified as cases of primary infertility, and couples who have had a biologic child previously are classified as cases of secondary infertility (Congress of the United States, Office of Technology Assessment. Infertility: Medical and Social Choices [OTA-BA-358], US Government Printing Office, 1988). It is important to note that these terms do not imply sterility, because many couples subsequently have children with or without medical treatment. Also, because epidemiologic studies of infertility involve measurement of the absence of conception rather than the presence of a specific disease, there is imprecision in the measurements used for research. Some investigators have extended the focus of study to include difficulty conceiving or carrying a pregnancy to term, and refer to impaired fecundity as a measure of the public health burden of fertility-related problems [1].