High-dose COCs have been shown to decrease the incidence of functional ovarian cysts.59 Low-dose COCs have not demonstrated a similar effect, although an attenuated effect may exist.60

An increased incidence of follicular cysts has been noted with LN implant (Norplant) use. The continuous low level of LN allows follicles to develop, and follicular cysts often result.60a These cysts only need to be evaluated sonographically or laparoscopically if they become large and painful. Similar to LN implants, the low dose of progestin in POPs allows follicles to develop and follicular cysts to form. However, one large cohort study evaluating ovarian cysts in COC users also looked at progestin-only pill users, and found no cases of follicular cysts in 219 person-months of observation.59 In contrast to POPs and implants, DMPA effectively suppresses follicular development and ovulation; thus, follicular cysts are rare among DMPA users.

Women using COCs have a markedly reduced risk of ovarian cancer, with increasing duration of use increasing the protective effect.61,62 and 63 A 10% decrease in risk is noted after 1 year of COC use, and a ˜50% decrease in risk is achieved after 5 years of use.62 This protective effect has been found to extend to women at highest risk of ovarian cancer, including women with BRCA-1 and BRCA-2 mutations64 (see also Chap. 223).