Although benign functional ovarian cysts are often self-limiting, they account for about 200,000 hospital admissions per year in the United States and cause considerable morbidity among women of reproductive age. Study results linking the use of high-dose oral contraceptives (OCs) to a reduced incidence of functional ovarian cysts have not been confirmed, and the effect of modern low-dose OCs is unclear. At least one study has linked tubal sterilization to an increased risk of functional ovarian cysts. To investigate the relationships between different forms of contraception and functional ovarian cysts, Holt and colleagues performed a case-control study of women 18 to 39 years of age who were enrolled in a large health maintenance organization in Washington State.
Medical records and radiology reports were used to identify all women who had functional ovarian cysts of at least 2.0 cm in diameter diagnosed between January 1990 and June 1994. Pregnant women and those with potentially pathologic cysts, including polycystic ovarian disease, were excluded from the study. The 586 women with cysts who agreed to participate in the study were matched by age to 757 control women in the same health maintenance organization. Women with a history of hysterectomy, oophorectomy, or infertility were not eligible to participate. All participants were interviewed about demographic, medical, and lifestyle factors, including contraceptive practices.
Women with functional ovarian cysts were less likely than control subjects to be married, to have a college education, and to have an income over $45,000, and were more likely than control women to smoke and have a body mass index greater than 25.7 kg per m2. Case subjects and control subjects had similar reproductive histories, except that case subjects had a significantly greater history of spontaneous miscarriage. OCs were used at some time by 87 percent of case subjects and 86 percent of control subjects, and were currently being used by 25 percent of case subjects and 28.6 percent of control subjects.
After controlling for significant variables, the overall odds ratio (OR) for current OC use was 0.72 (see accompanying table) compared with no contraception, nonsurgical contraception, or nonhormonal contraception methods. In subanalyses, the OR for OCs containing 35 mcg of ethinyl estradiol was 0.69, compared with 0.79 for OCs containing lower doses of estrogen, and 0.76 for multiphasic OCs. The overall OR for sterilization was 1.70, and this was higher in women who had undergone postpartum sterilization than in women who had interval sterilization (2.55 compared with 1.50). The strongest association was with sterilization before age 30 (OR, 3.54; confidence interval [CI], 1.24 to 10.11), but the time from sterilization was not associated with risk of functional ovarian cysts.
The authors conclude that current OC use is associated with a modest decline in the risk of development of functional ovarian cysts, but that the use of modern low-dose OCs has little or no clinical effect on the likelihood of developing functional ovarian cysts. Conversely, sterilization, especially at a young age, appears to significantly increase the risk of functional ovarian cysts. This finding confirms those of an earlier study in which the risk of ovarian cysts was doubled (from 12.4 percent to 24.1 percent) in women who had been sterilized. Because surgical sterilization is the most common form of contraception in the United States, the authors call for further studies to confirm this increased risk.