Contraception selection, efficacy, and risks

Contraceptive effectiveness is determined by several factors, including drug or device efficacy, individual fecundability, coital frequency, and user adherence and continuation.

Oral contraceptive pills are the most frequently used reversible contraceptives, but intrauterine devices and subdermal implants have the highest efficacy, according to a review in the Journal of the American Medical Association.1

The review also concluded that risks are lowest in progestin-only and nonhormonal methods; however, optimal contraceptive selection must consider patient values and preferences.

The authors noted that roughly 87% of women in the US use contraception during their lifetime, with oral contraceptive pills representing 21.9% of all current contraception use. But use of long-acting methods like intrauterine devices and subdermal implants have increased dramatically over the years, from 6% in 2008 to 17.8% in 2016.

Contraceptive effectiveness is determined by several factors, including drug or device efficacy, individual fecundability, coital frequency, and user adherence and continuation.

Pregnancy rates for those using oral contraceptives range from 4% to 7% annually, compared to failure rates of less than 1% per year for long-acting methods.

Regarding safety, estrogen-containing methods, such as combined oral contraceptive pills, increase the risk of venous thrombosis from 2 to 10 venous thrombotic events per 10,000 women-years to 7 to 10 venous thrombotic events per 10,000 women-years.

Due to concern for increased rates of thrombosis, the authors think combined hormonal contraceptives are not likely to become available over the counter (OTC), but efforts to allow progestin-only pills OTC are advancing.

Meanwhile, progestin-only and nonhormonal methods, like implants and condoms, are linked to rare and serious risks.

Hormonal contraceptives, wrote the authors, “can improve medical conditions associated with hormonal changes related to the menstrual cycle, such as acne, endometriosis, and premenstrual dysphoric disorder.”

Combined hormonal contraceptives also protect against endometrial and ovarian cancer; however, they pose an increased risk of early breast cancer diagnosis in current or recent users within the past 6 months, with an incidence of 68 cases per 100,000 person-years vs 55 cases per 100,000 nonuser-years.

On the other hand, there are no associations of past contraceptive use with increased rates of cancer or mortality.

Although obesity adversely impacts contraceptive steroid levels, it is difficult to determine whether it affects contraceptive effectiveness, according to the authors, noting the main reason for contraceptive failure as suboptimal adherence. They also emphasized that using any contraceptive method, regardless of weight, prevents more pregnancies than not using a method at all.

No high-quality evidence exists to support the recommendation of prior guidance to restrict the use of intrauterine devices by teenagers, nonmonogamous or unmarried, and nulliparous women. “None of these characteristics are true contraindications,” wrote the authors.

Presently, the United States Food and Drug Administration lacks approved contraceptive options for men, except condoms, according to the authors. Male contraceptive methods in current evaluation attempt to suppress sperm count to <1 million/mL, via a testosterone-plus-progestin topical gel.

The best contraceptive selection, however, entails patient and clinician discussion of the patient’s tolerance for risk of pregnancy, menstrual bleeding changes, and other risks, as well as the patient’s personal values and preferences.

Patients may value certain features of a method more than efficacy, such as the route of administration or bleeding patterns, thus perhaps favoring a slightly higher risk of unplanned pregnancy to avoid other adverse effects.

Reference

  1. Teal S, Edelman A. Contraception selection, effectiveness, and adverse effects: a review. JAMA. Published online December 28, 2021. doi:10.1001/jama.2021.21392