Effectiveness is a number with a footnote

The Centers for Disease Control and Prevention says a contraceptive should be chosen through voluntary, informed choice. The factors it lists are safety, effectiveness, availability (including cost and whether you can actually get it), side effects, user control, reversibility, and how easy the method is to stop. No method on that list is best for every person. The FDA's public birth control chart states that the only sure way to avoid pregnancy is not to have sex. Every method below has a failure rate, and the rate that matters for daily life is typical use, which counts people who miss pills, put a condom on late, or get a shot a week late.

The figures below are the typical-use failure rates on the CDC's contraception page (August 6, 2024), drawn from Contraceptive Technology, 22nd edition (Bradley, Polis, Micks, and Steiner, 2023). They are pregnancies in the first year per 100 users.

Methods that do not depend on a daily habit

  • Etonogestrel implant. A thin rod under the skin of the upper arm, progestin released for 3 years. Typical-use failure rate: 0.1%.
  • Levonorgestrel IUD. A T-shaped device in the uterus, releasing a small amount of progestin, left in place 3 to 8 years depending on the brand. Typical-use failure rate: 0.1% to 0.4%. Brand differences are in the IUD guide.
  • Copper IUD. No hormone, up to 10 years. Typical-use failure rate: 0.8%.
  • Copper IUD as emergency contraception. The CDC says it can be inserted within 5 days of unprotected sex. Emergency contraception is not a standing method. Pills used after sex can be taken up to 5 days later, and they work better the sooner they are taken. Some are over the counter and some are prescription.

The CDC's 2024 Selected Practice Recommendations note that fewer than 1 IUD user out of 100 becomes pregnant in the first year of typical use, and that IUDs can be used at any reproductive age, including by adolescents and by people who have not had a child.

Methods you have to keep using

  • Injection (depot medroxyprogesterone acetate). A progestin shot every three months, in a clinic or self-injected. Typical-use failure rate: 4%.
  • Combined pill, progestin-only pill, patch, and vaginal ring. Typical-use failure rate: 7% for each. The combined pill, patch, and ring contain estrogen and progestin. The progestin-only pill does not. The patch is a new one each week for three weeks, then a week off. The ring is worn for three weeks and removed for the bleeding week, in the schedule the CDC describes.
  • External (male) condom. Typical-use failure rate: 13%. Latex condoms also help prevent HIV and other STIs. Lambskin condoms may prevent pregnancy and may not prevent STIs, including HIV.
  • Internal (female) condom. Typical-use failure rate: 21%. The CDC says these might help prevent STIs.
  • Diaphragm. 17%. Cervical cap. 22%. Sponge. 17%. Spermicides and vaginal pH regulators. 21%.
  • Fertility awareness–based methods. The CDC gives a range, 2% to 23%, because the methods are not one technique. If cycles are regular, there are about nine or more fertile days each month. Avoiding pregnancy means no sex on fertile days, or a barrier method on those days.
  • Lactational amenorrhea. Breastfeeding can work as birth control only when three conditions are all true: no menstrual periods since the birth, full or nearly full breastfeeding, and less than 6 months since delivery. When any condition fails, another method is needed.
  • Tubal surgery. Typical-use failure rate: 0.5%. Vasectomy. 0.15%, and another method is needed until a clinician confirms the sperm count is zero, which takes about 12 weeks.

Most of these methods do not protect against STIs or HIV. The CDC's advice is condoms, alone or with another method, and pre-exposure prophylaxis when HIV prevention is the goal. A very effective IUD plus a condom is a reasonable pairing if both pregnancy and infection are concerns. One method rarely solves both.

Estrogen is not available to everyone

The CDC's public page says that if you are older than 35 and smoke, or you have a history of blood clots or breast cancer, a doctor may advise you not to take the combined pill. The 2024 U.S. Medical Eligibility Criteria are more precise. Category 4 means an unacceptable health risk if that method is used. For combined hormonal methods (pill, patch, and ring), category 4 includes:

  • Age 35 or older and smoking 15 or more cigarettes a day (fewer than 15 cigarettes at that age is category 3)
  • Migraine with aura
  • Known thrombophilia, such as factor V Leiden, prothrombin gene mutation, protein C deficiency, protein S deficiency, antithrombin deficiency, or antiphospholipid syndrome
  • A higher-risk history of deep-vein thrombosis or pulmonary embolism (for example, a clot tied to estrogen or pregnancy, an unexplained clot, or recurrent clots) when not on anticoagulant therapy
  • Breastfeeding less than 21 days after birth

A lower-risk history of a clot can be category 3 rather than 4, and someone on treatment-dose blood thinners is classified differently again. The consumer sentence "a history of blood clots means no estrogen" is the right reason to ask, and the wrong sentence to treat as a complete rule. Bring the actual history. Progestin-only methods and the copper IUD are often the alternatives a clinician considers when estrogen is a poor fit. This page is not assigning you a category.

How soon you can get pregnant after you stop

Reversibility is one of the CDC's stated decision factors. It is not the same for every method. The FDA label for Depo-Provera CI says return of ovulation and fertility is likely to be delayed after the shot is stopped. In the U.S. study described on the label, data were available for 61% of women who stopped in order to become pregnant. Of 188 who discontinued to become pregnant, 114 became pregnant. Life-table analysis suggested that, among those who do conceive, 68% may conceive within 12 months of the last injection, 83% within 15 months, and 93% within 18 months. The median time to conception for those who conceive was 10 months after the last injection, with a range of 4 to 31 months, unrelated to how long they had used the shot. Thirty-nine percent of that group were lost to follow-up or changed their minds, so the label is reporting a selected group. If you want a pregnancy within a few months, say so before you start the injection.

IUDs and the implant are removed when you want them gone. The CDC lists ease of removal as its own factor because "long-acting" should not mean "stuck with it." Removal of an IUD is a short office procedure. Fertility plans after removal are individual. Do not assume a method is permanent unless you had a sterilization procedure.

A way to walk into the visit

Write down four answers before you go:

  1. How unacceptable is a pregnancy in the next year? If the answer is "devastating," look first at the implant and the IUDs, where typical-use failures sit under 1 per 100.
  2. Do you need STI protection as well? If yes, condoms stay in the plan no matter what else you choose.
  3. Is there a reason to avoid estrogen: migraine with aura, smoking at 35 or older, a clot, a thrombophilia, recent birth while breastfeeding? Say it out loud. Do not wait to be asked.
  4. When might you want a pregnancy? A shot with a median 10-month wait among those who conceive is a different choice from a condom you can stop tonight.

Side effects are method-specific and are a reason people quit. The CDC page names irregular bleeding, breast tenderness, headache, and nausea among experiences with various hormonal methods. A method you will not use has the failure rate of no method. Tell the clinician what you already hated about a past method so they do not hand you the same experience in a new package.

You can line the same methods up on this site's contraception comparison before the appointment. The tool is a worksheet. The prescription, the device, and the eligibility decision happen in the exam room.

Which of the four questions above is the one you have been avoiding?

Sources

Educational only. Eligibility for estrogen, emergency contraception timing, and removal of a device are clinical decisions.