How Birth Control Works: Hormonal and Non-Hormonal Options

The Fundamentals of Contraception

Birth control, or contraception, refers to any method used to prevent pregnancy. Methods work through several mechanisms: preventing ovulation, blocking sperm from reaching an egg, preventing fertilization, or preventing a fertilized egg from implanting in the uterus. The effectiveness of each method is described in two ways — perfect use (when the method is used correctly and consistently every time) and typical use (reflecting real-world use including human error).

The most effective methods are those that require the least user effort once in place, such as intrauterine devices and implants. These are called long-acting reversible contraceptives (LARCs) and have failure rates below 1 percent with typical use. User-dependent methods such as the pill, patch, or condoms have higher typical-use failure rates because missing doses or incorrect use reduces effectiveness.

Choosing a contraceptive method involves weighing effectiveness, side effect profile, convenience, reversibility, protection against sexually transmitted infections (STIs), and personal health history. Only barrier methods — particularly condoms — provide meaningful protection against STIs in addition to pregnancy prevention.

Combined Hormonal Contraceptives

Combined hormonal contraceptives contain both estrogen and progestogen (a synthetic form of progesterone). The combination pill is taken daily and works primarily by suppressing ovulation. Estrogen and progestogen together inhibit the pituitary gland from releasing the hormones FSH and LH, preventing follicle development and ovulation. The progestogen component also thickens cervical mucus, making it harder for sperm to pass, and thins the uterine lining.

The contraceptive patch (worn on the skin and changed weekly) and the vaginal ring (inserted monthly) deliver the same hormones via different routes, allowing continuous absorption and avoiding the daily pill requirement. All combined methods have a typical-use failure rate of about 7 to 9 percent per year, largely due to missed pills or late patch changes.

Benefits of combined hormonal contraceptives beyond pregnancy prevention include reduced menstrual bleeding and cramps, improvement of acne and PCOS symptoms, and reduced risk of ovarian and endometrial cancer with long-term use. They are not appropriate for individuals who smoke and are over 35, those with a history of blood clots, or those with certain cardiovascular conditions, as estrogen increases the risk of venous thromboembolism and stroke in these groups.

Progestogen-Only Methods

Progestogen-only methods are available in several forms. The mini-pill is taken daily and works mainly by thickening cervical mucus and, in some formulations, suppressing ovulation. It must be taken at the same time every day and has a slightly narrower window for missed doses than the combined pill. It is suitable for individuals who cannot use estrogen, including those who are breastfeeding, those with migraines with aura, and those with cardiovascular risk factors.

The progestogen-only implant is a small flexible rod inserted under the skin of the upper arm by a healthcare provider. It releases a low, continuous dose of progestogen and provides highly effective contraception for up to three years with a failure rate below 0.1 percent. The hormonal IUD (intrauterine device) releases progestogen locally in the uterus, thickening cervical mucus and thinning the endometrium. Hormonal IUDs are among the most effective methods available and last three to eight years depending on the type.

The progestogen-only injectable (such as Depo-Provera) is given every 12 to 13 weeks. It strongly suppresses ovulation and is highly effective. A notable consideration is that fertility may take six to 18 months to return after stopping injections, unlike most other hormonal methods where fertility returns promptly. All progestogen-only methods may cause irregular bleeding, which is the most common reason individuals discontinue them.

Intrauterine Devices (IUDs)

IUDs are small T-shaped devices placed inside the uterus by a healthcare provider. Two types are available: hormonal and copper. The hormonal IUD, discussed above, releases progestogen locally. The copper IUD is non-hormonal and works by releasing copper ions, which are toxic to sperm and impair their ability to fertilize an egg. The copper IUD can also be used as emergency contraception when inserted within five days of unprotected sex.

Copper IUDs are among the most effective forms of contraception, with a failure rate below 0.8 percent per year, and can remain in place for 10 to 12 years. They do not affect hormones, making them appropriate for those who prefer a completely hormone-free option or who cannot use hormones. The main drawback is that they can increase menstrual bleeding and cramping, particularly in the first few months after insertion.

IUD insertion involves a brief clinic procedure and may cause cramping during and after insertion. Serious complications including expulsion (the IUD moving out of position) and uterine perforation are rare. IUDs are reversible — fertility typically returns quickly after removal, making them suitable even for individuals who plan to conceive in the future.

Barrier Methods and Spermicides

Barrier methods physically prevent sperm from reaching the egg. Male (external) condoms, when used correctly and consistently, have a typical-use failure rate of about 13 percent per year. They are the only contraceptive method that also provides significant protection against STIs, including HIV, chlamydia, and gonorrhea, making them valuable even when combined with other contraceptive methods.

Female (internal) condoms are an alternative barrier method that the receptive partner can insert before sex. They provide similar STI protection and have a typical-use failure rate of about 21 percent. The diaphragm and cervical cap are reusable barrier devices inserted before intercourse to cover the cervix. They are used with spermicide, a chemical that immobilizes sperm, and require a fitting from a healthcare provider. Their typical-use failure rates are higher than other methods, particularly for those who have given birth vaginally.

Spermicide used alone has a high failure rate and is not recommended as a primary contraceptive method. Contraceptive sponges combine a physical barrier with spermicide and are available over the counter, but their failure rate in those who have previously given birth is considerably higher than in those who have not.

Permanent and Emergency Contraception

Surgical sterilization provides permanent contraception. Tubal ligation (colloquially called having the tubes tied) blocks or removes the fallopian tubes, preventing sperm from reaching an egg. Vasectomy, the male equivalent, cuts or blocks the vas deferens. Both procedures are considered irreversible and are highly effective — though reversal surgeries exist, success rates are variable and decrease over time. Sterilization does not affect hormones and has no effect on menstruation or libido.

Emergency contraception (EC) reduces the risk of pregnancy after unprotected sex. Levonorgestrel pills (Plan B and similar products) work by delaying or preventing ovulation and are most effective when taken within 72 hours, though they retain some efficacy up to 120 hours. Ella (ulipristal acetate) is more effective than levonorgestrel EC, especially taken closer to 120 hours. The copper IUD, as noted above, is the most effective form of EC. Emergency contraception does not terminate an established pregnancy and should not be confused with medication abortion. Natural family planning methods, which rely on tracking fertility signs to time sexual activity, are included here for completeness but require significant training and consistent application to be effective.