Does contraception modify the risk of endometriosis?

Long episodes of regular, prolonged, abundant menstrual flows are generally agreed to increase the risk of endometriosis. Since oral oestrogen-progestogen combinations reduce and intra-uterine contraceptive devices increase menstrual flow, an effect on the risk of development of endometriosis in women utilizing these forms of contraception could be expected. Analysis of the most recent epidemiological observations shows no consensus on a possible relationship between use of cyclic oral contraceptives and endometriosis, with an increase, a decrease, and no effect on the risk of developing the disease all being reported. A lower relative risk of endometriosis in previous users of the intrauterine contraceptive device was only found in two series, most of the other data suggesting a rise in risk or no effect. Further studies on the relationship between type of contraception and endometriosis are needed to demonstrate whether the risk of development of the disease could be influenced, and whether well tolerated, relatively inexpensive, long-term treatment might be available for symptomatic patients not desiring offspring.