[Reproductive activities as a risk factor of endometriosis]

A case-control study, involving 203 cases of pelvic endometriosis and 406 randomly selected and age-matched community controls, was conducted. The results were as following: 1) A decreased risk for endometriosis was found to be related to pregnancy. The relative risk was 0.34 for para 1 and 0.08 for para 2 or more. A similar tendency was also showed in the analysis of gravidity, but this protective effect totally disappeared after adjustment for parity. Therefore, it may be revealed that it is the parity but not the gravidity which protects the women against the endometriosis. 2) There was an increased risk of 15.35 for endometriosis in women with infertility. 3) No relation emerged with age at first pregnancy to the occurrence of endometriosis as indicated in the literature. 4) The frequency of induced abortion was 42.4% in the cases and that was 63.7% in the controls. The association with the risk of the disease adjusted for education, menstruation, parity and contraception was not significant by a attentive stratification the data. 5) Two groups were relatively similar with respect to recorded condom and oral contraceptive use. However, more cases than controls did not use any contraception or only used rhythm method and coitus interruptus, and more controls than cases used an intrauterine device. The results of multivariate analysis did not approve of opinion that IUD is a risk factor of endometriosis. The results did not negate the likelihood of diminished chance of developing endometriosis in women with using oral contraceptives.