Endometriosis and infertility: a laparoscopic study of endometriosis among fertile and infertile women.

To test the widely accepted--but not well-supported--impression that endometriosis and infertility are associated, we compared the prevalence of endometriosis visualized at laparoscopy in 100 patients being evaluated for infertility and in 200 fertile control subjects (two age-matched to each patient) undergoing tubal ligation. The extent of endometriosis and adhesions noted in the operative reports was classified according to the system proposed by The American Fertility Society. Endometriosis was found in 21 of the 100 infertile patients--mild in 11, moderate in 8, severe in 2. It was found in 4 (2%) of the 200 controls and was mild in all 4. Thus, endometriosis is more often present, and more often severe, among infertile patients. The risk of infertility was estimated to be almost 20 times greater with endometriosis than without. These data support the clinical impression that an association exists.