Summary of Evidence

Oral Contraceptives: Benefits
Oral Contraceptives: Harms
Prophylactic Oophorectomy: Benefits
Prophylactic Oophorectomy: Harms

Note: Separate PDQ summaries on Ovarian Cancer Screening and Ovarian Epithelial Cancer Treatment are also available.

Based on solid evidence, oral contraceptive use is associated with a decreased risk of developing ovarian cancer.

Description of the Evidence

• Study Design: Evidence obtained from multiple case-control and cohort studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: A relative risk (RR) reduction of about 50% overall with a dose response ranging from 5% to 10% RR reduction per year of use to maximum RR reductions of up to 80%.
• External Validity: Good.

Based on solid evidence, combined current use of estrogen/progestogen oral contraceptive use is associated with an increased risk of venous thromboembolism. Oral contraceptives are not associated with a long-term increased risk of breast cancer but may be associated with a short-term increased risk while a woman is taking oral contraceptives. The risk of breast cancer declines with time since last use.

Description of the Evidence

• Study Design: Evidence obtained from observational studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: The risks may vary by preparation. Overall, the absolute risk of venous thromboembolism is about three events per 10,000 women per year while taking oral contraceptives. The risk is increased by smoking. Breast cancer risk among long-term (>10 years) current users is estimated at one extra case per year per 100,000 women. The risk dissipates with time since last use.
• External Validity: Good.

Based on solid evidence, prophylactic bilateral oophorectomy is associated with a decreased risk of ovarian cancer. Peritoneal carcinomatosis has been reported following prophylactic removal of the ovaries. Prophylactic oophorectomy, along with salpingo-oophorectomy, is generally reserved for women at high risk of developing ovarian cancer, such as women who have a deleterious mutation in a BRCA1 or BRCA2 gene.

Description of the Evidence

• Study Design: Evidence obtained from multiple case-control and cohort studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: 90% reduction in risk of ovarian cancer observed among women with a BRCA1 or BRCA2 mutation.
• External Validity: Good.

Based on solid evidence, prophylactic oophorectomy among women who are still menstruating at the time of surgery is associated with infertility, vasomotor symptoms, decreased sexual interest, vaginal dryness, urinary frequency, decreased bone mineral density, and increased cardiovascular disease.

Description of the Evidence

• Study Design: Cohort and case-control studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: Reported prevalence of vasomotor symptoms varies from 41% to 61.4% among women who underwent oophorectomy prior to natural menopause. Women with bilateral oophorectomy who did not take hormone therapy were twice as likely to have moderate or severe hot flashes compared to women undergoing a natural menopause. The RR of cardiovascular disease among women with bilateral oophorectomy and early menopause was 4.55 (95% confidence interval, 2.56–9.01).
• External Validity: Good.