A contraceptive is anything used to prevent pregnancy. Contraceptives work in one of a few basic ways: blocking sperm from reaching an egg, stopping the body from releasing an egg in the first place, or permanently closing off the reproductive pathway. Options range from a daily pill to a device that lasts a decade, and choosing between them comes down to effectiveness, convenience, side effects, and whether you also want protection from sexually transmitted infections.
How Contraceptives Prevent Pregnancy
Every contraceptive method falls into one of four categories based on how it works in the body.
- Barrier methods physically keep sperm and egg apart. Condoms, diaphragms, and cervical caps all do this.
- Hormonal methods change the body’s hormone balance to stop ovulation (the release of an egg), thicken cervical mucus so sperm can’t swim through, or thin the uterine lining. Pills, patches, injections, implants, and hormonal IUDs all use this approach.
- Intrauterine devices (IUDs) are small devices placed inside the uterus. Hormonal versions release a hormone locally. The copper version creates an environment that’s toxic to sperm, without using hormones at all.
- Sterilization is a surgical procedure that permanently blocks the path sperm or eggs travel. In women, this means sealing or cutting the fallopian tubes. In men, it means cutting or blocking the tubes that carry sperm out of the testes.
Hormonal Methods
Hormonal contraceptives use one or two synthetic hormones: a form of estrogen, a form of progestin, or both. Combined methods (estrogen plus progestin) primarily work by preventing ovulation and thickening cervical mucus. Progestin-only methods may or may not stop ovulation consistently, but they reliably thicken cervical mucus enough to block sperm from reaching the egg.
The pill is the most well-known option. Combined pills contain both hormones; the “mini-pill” contains only progestin, which can matter for people who can’t take estrogen. Beyond pills, hormonal contraceptives come in several other forms. The patch sticks to the skin and releases estrogen and progestin through the bloodstream, replaced weekly. The vaginal ring sits inside the vagina and releases the same two hormones, typically swapped out monthly. The injection delivers progestin into the arm or buttock every three months. And the implant, a thin rod inserted under the skin of the upper arm, releases progestin steadily for three years.
With typical, real-world use, about 9 out of 100 people on the pill become pregnant in the first year. With perfect use (never missing a dose, taking it at the same time daily), that drops to fewer than 1 in 100. The injection has a typical-use failure rate of about 6%, largely because people sometimes miss their appointment window.
Long-Acting Reversible Contraception
IUDs and implants are grouped together as “long-acting reversible contraception,” or LARC. They’re the most effective reversible methods available because they don’t depend on remembering to do anything after the initial placement.
The copper IUD contains no hormones. It prevents sperm from reaching and fertilizing the egg, and it can stay in place for up to 10 years. Hormonal IUDs release progestin directly into the uterus, which thickens cervical mucus and thins the uterine lining. Depending on the specific device, hormonal IUDs last 3 to 5 years. The hormonal implant, placed under the arm’s skin in a quick office visit, lasts 3 years.
Fewer than 1 in 100 people become pregnant during the first year of IUD use. Hormonal IUDs have a failure rate of roughly 0.1 to 0.2%, while the copper IUD’s rate is slightly higher at 0.5 to 0.8%. The implant matches the hormonal IUD at about 0.1%. These numbers are nearly identical for typical and perfect use, since there’s no daily action to forget.
Barrier Methods
Barrier methods work by physically preventing sperm from entering the uterus. The most common is the external (male) condom. With typical use, about 18 out of 100 people using condoms as their only method become pregnant in a year. With perfect use, that drops to about 2 in 100. The gap is large because condoms can slip, break, or simply not get used every single time.
Condoms have one major advantage no other contraceptive offers: STI protection. When used consistently and correctly, external latex condoms reduce the risk of HIV, chlamydia, gonorrhea, hepatitis B, herpes, HPV, and syphilis. Internal (female) condoms also provide STI protection, though the evidence is more limited. No other contraceptive method, whether it’s the pill, an IUD, an implant, or sterilization, protects against sexually transmitted infections. Spermicides used alone are not recommended for STI prevention and can actually increase HIV risk by irritating tissue.
Emergency Contraception
Emergency contraception is a backup option used after unprotected sex, not a routine method. It works primarily by delaying or preventing ovulation and thickening cervical mucus. Two types of emergency contraceptive pills exist. One contains a single hormone and is available over the counter. The other requires a prescription and tends to be more effective in the 3-to-5-day window after unprotected sex. Both types should be taken as soon as possible, and both can work up to 5 days afterward, though effectiveness declines with each passing day. The copper IUD can also serve as emergency contraception when inserted within 5 days, and it doubles as ongoing birth control for years afterward.
Permanent Sterilization
Sterilization is intended to be permanent. For women, tubal ligation (having the fallopian tubes cut, tied, or sealed) is effective immediately. About 0.5 out of 100 people with tubal surgery become pregnant in the first year. For men, a vasectomy cuts or blocks the tubes that carry sperm. Its typical failure rate is even lower, at about 0.15 per 100 in the first year. Once a man achieves a zero sperm count after the procedure, the chance of pregnancy drops to roughly 1 in 2,000.
Recovery differs between the two. After tubal surgery, no additional contraception is needed right away. After a vasectomy, sperm can still be present in the reproductive tract for weeks. A semen analysis is recommended 8 to 16 weeks later to confirm success, and condoms or abstinence should be used until that confirmation comes back clear.
Effectiveness at a Glance
The gap between “typical use” and “perfect use” tells you how much a method depends on human consistency. Methods you don’t have to think about daily have almost no gap. Methods that require action every time you have sex or every day have a wide one.
- Hormonal IUD: 0.2% failure rate (typical and perfect use are the same)
- Implant: 0.1% failure rate
- Female sterilization: 0.5%
- Vasectomy: 0.15%
- Injection: 6% typical, 0.2% perfect
- Pill: 9% typical, 0.3% perfect
- Male condom: 18% typical, 2% perfect
- Withdrawal: 22% typical, 4% perfect
- Spermicides alone: 28% typical, 18% perfect
Health Benefits Beyond Pregnancy Prevention
Hormonal contraceptives are frequently prescribed for reasons that have nothing to do with preventing pregnancy. Combined pills can make periods more regular, lighter, and less painful. They’re used to treat endometriosis-related pelvic pain, premenstrual syndrome, and acne. The vaginal ring is effective for severe PMS and painful periods. The patch has similar effects on menstrual symptoms and may also help with acne.
Longer-term, combined oral contraceptives reduce the risk of certain cancers. Ovarian cancer risk drops by roughly 20% for every five years of use. An 18% risk reduction has been reported for colorectal cancer among people who have used oral contraceptives. The risk of endometrial cancer is also lower. Hormonal IUDs, because they deliver high concentrations of hormone directly to the uterine lining, are used to treat abnormal uterine thickening. Combined pills can also prevent ovarian cysts by suppressing ovulation, and they’ve been shown to reduce the incidence of ectopic pregnancies.
These secondary benefits mean that many people continue using hormonal contraceptives even when pregnancy prevention isn’t their primary concern.