Essential Knowledge

© 2011 James Byrnes, Courtesy of Photoshare

When used consistently and correctly, oral contraceptives (OCs) are among the most effective methods available for preventing unintended pregnancies. They are safe for most women of reproductive age and are used by more than 100 million women worldwide. The Essential Knowledge section of the Oral Contraceptives Toolkit offers evidence-based information and reference materials on the safety, effectiveness, acceptability, and medical eligibility criteria for the different types of oral contraceptives among women of reproductive age and special populations within this group including young people and people living with HIV. 

Key Points about Combined Oral Contraceptives and Progestin-Only Pills

  • COCs are pills, taken once a day, that contain low doses of progestin and estrogen. This prevents the release of eggs from the ovaries (ovulation). POPs, also taken once a day, contain low doses of progestin. This not only prevents ovulation but also thickens the cervical mucus, blocking sperm from meeting an egg.
  • When taken correctly, COCs and POPs are highly effective, with less than 1 pregnancy per 100 women over the first year.
  • With typical use, about 8 per 100 women using COCs will become pregnant over the first year. This means that 92 of every 100 women will not become pregnant.
  • In addition to pregnancy prevention, COCs offer a number of health benefits. COCs:
    • protect against endometrial and ovarian cancer and pelvic inflammatory disease
    • might help protect against ovarian cysts and iron-deficiency anemia
    • can reduce menstrual cramps and bleeding problems, ovulation pain, excess facial or body hair, and symptoms of polycystic ovarian syndrome and endometriosis
  • Once women stop using COCs or POPs, fertility returns immediately.
  • COCs and POPs do not protect against sexually transmitted infections (STIs), including HIV. To protect against STIs, including HIV, women or couples who want to use COCs or POPs should use condoms consistently and correctly in addition to the oral contraceptives.
  • Side effects of COCs and POPs can include changes in bleeding patterns, headaches, dizziness, nausea, breast tenderness, weight change, mood changes, abdominal pain, and acne. On very rare occasions, COCs can increase the risk of blood clots, stroke, and heart attack.

Please visit the Emergency Contraception Toolkit for similar information and materials on emergency contraceptive pills, which help prevent pregnancy when taken up to five days after unprotected sex.

Do you have a comment about this Toolkit or a resource you'd like to suggest for inclusion? Share your suggestions, comments, and questions by sending a message through the feedback form.