The prevalence of subfertility: a review of the current confusion and a report of two new studies.

The difficulties inherent in measuring the prevalence of subfertility are discussed. Four subtypes of subfertility are defined, enabling comparisons to be made between the widely different approaches previously reported. A detailed assessment was made of the prevalence of subfertility in two different samples of British women aged 25 to 44 years, using interviews, postal questionnaires, and medical record searches. Data were collected on 872 women from a general practice and 702 hospital patients. The combined data showed that 24% of all women attempting to conceive experience an episode of subfertility at some stage in their reproductive life. Thirteen percent experience this in attempting to conceive their first child, and 17% when attempting to conceive a subsequent child. Three percent of women are involuntarily childless and 6% of parous women are not able to have as many children as they would wish.