The incidence of endometriosis is not known, since the only reliable way of determining its presence is at surgery or autopsy. Surgical incidence is biased by the selection process bringing the patient to the operating room. No large cadaver study examining autopsy specimens for endometriosis has reported data that has been widely accepted.
Despite uncertainty, widely used numbers for the incidence of endometriosis include 3-10% of all reproductive age women and 25-40% of all women with an infertility problem. The “Public testimony to the US Senate Committee on Labor and Human Resources, Subcommittee on Aging” report in 1993 estimated that about 5 million women in the USA are affected by endometriosis.
The literature on the prevalence of endometriosis in selected groups of women suggest a 2% rate for those undergoing elective tubal sterilization, an 8-12% rate for those undergoing hysterectomy, a 30% rate for those undergoing operative laparoscopy and a 55% rate for teenagers undergoing diagnostic laparoscopy for pelvic pain.
In 1987, the “National Center for Health Statistics” report on hysterectomies performed in the USA between 1965 and 1984 described about 2 million US women following hysterectomy with a diagnosis of endometriosis. An interesting finding from this report was that the number of women with endometriosis having a hysterectomy increased steadily throughout the target time period, with less than 150,000 women in 1965-67 and greater than 350,000 women in 1982-84. This increase was not fully accounted for by an increase in hysterectomies in general and occurred during a time when increasingly conservative management for endometriosis became popular. Therefore, the increase may reflect an increase in the incidence or severity of endometriosis in the USA.