Sexual activity, contraception, and reproductive factors in predicting endometriosis.

To examine the belief that women with endometriosis have "voluntarily" delayed childbirth, the authors used a case-control approach to assess the relation between sexual, contraceptive, and reproductive factors and endometriosis. A total of 104 laparoscopically confirmed newly diagnosed cases of endometriosis were identified from a gynecologic specialty clinic in western New York state in 1987. Two control groups were used: 1) 100 friend controls, and 2) 98 medical controls. No differences were found between study groups on use of reliable birth control, use of birth control before a first pregnancy, age at first intercourse, frequency of intercourse, decisions to delay pregnancy, age at first pregnancy, or measures of body size. Cases were older than medical controls by about 1 year when they first began using birth control (19.8 vs. 18.6 years, p < 0.05). Cases were also 1 year older than friend controls when they began regular intercourse (20.9 vs. 19.5 years, p < 0.005) and at first marriage (22.8 vs. 21.7 years, p < 0.05). A larger percentage of cases than friend controls were never pregnant (p < 0.0001) and were more likely to have problems becoming pregnant (p < 0.0001). Results, overall, do not support simplistic assumptions that characterize endometriosis patients as career women who voluntarily delay pregnancy. Rather, the results point to a complex relation between endometriosis and reproductive, sexual activity, and fertility-related factors.