Contraception (birth control) prevents pregnancy by interfering with the normal process of ovulation, fertilization, and implantation. There are different kinds of birth control that act at different points in the process.
Intrauterine Methods An intrauterine device (IUD), also known as an intrauterine system (IUS), is a small, T-shaped device that is inserted into the uterus to prevent pregnancy. A health care provider inserts the device. An IUD can remain in place and function effectively for many years at a time. After the recommended length of time, or when the woman no longer needs or desires contraception, a health care provider removes or replaces the device.
Combined Hormonal Methods Combined hormonal methods contain a synthetic estrogen (ethinyl estradiol) and one of the many progestins approved in the United States. All of the products work by inhibiting ovulation and thickening cervical mucus. The combined estrogen/progestin drugs can be delivered by pills, a patch, or a vaginal ring. The combined hormonal methods have some medical risks, such as blood clots, that are associated with the synthetic estrogen in the product.
Short-Acting Hormonal Methods Hormonal methods of birth control use hormones to regulate or stop ovulation and prevent pregnancy. Ovulation is the biological process in which the ovary releases an egg, making it available for fertilization. Hormones can be introduced into the body through various methods, including pills, injections, skin patches, transdermal gels, vaginal rings, intrauterine systems, and implantable rods. Depending on the types of hormones that are used, these methods can prevent ovulation; thicken cervical mucus, which helps block sperm from reaching the egg; or thin the lining of the uterus.
A copper IUD prevents sperm from reaching and fertilizing the egg, and it may prevent the egg from attaching in the womb. If fertilization of the egg does occur, the physical presence of the device prevents the fertilized egg from implanting into the lining of the uterus. A hormonal IUD or IUS releases a progestin hormone (levonorgestrel) into the uterus. The released hormone causes thickening of the cervical mucus, inhibits sperm from reaching or fertilizing the egg, thins the uterine lining, and may prevent the ovaries from releasing eggs.
Combined oral contraceptives (COCs, "the pill"). COCs contain a synthetic estrogen and a progestin, which functions to inhibit ovulation. A woman takes one pill daily, preferably at the same time each day. Contraceptive patch. This is a thin, plastic patch that sticks to the skin and releases hormones through the skin into the bloodstream. The patch is placed on the lower abdomen, buttocks, outer arm, or upper body. Vaginal ring. The ring is thin, flexible, and approximately 2 inches in diameter. It delivers a combination of ethinyl estradiol and a progestin. The ring is inserted into the vagina, where it continually releases hormones for 3 weeks.
Injectable birth control. This method involves injection of a progestin, Depo-Provera® (depot medroxyprogesterone acetate [DMPA]), given in the arm or buttocks once every 3 months.Progestin-only pills (POPs). A woman takes one pill daily, preferably at the same time each day. POPs may interfere with ovulation or with sperm function. POPs thicken cervical mucus, making it difficult for sperm to swim into the uterus or to enter the fallopian tube.
Barrier Methods Designed to prevent sperm from entering the uterus, barrier methods are removable and may be an option for women who cannot use hormonal methods of contraception. Barrier methods have a typical failure rate of 12% to 28% depending on the method.
Sterilization is a permanent form of birth control that either prevents a woman from getting pregnant or prevents a man from releasing sperm. A health care provider must perform the sterilization procedure, which usually involves surgery. These procedures usually are not reversible.
Emergency contraception can be used after unprotected intercourse or if a condom breaks.
Male condoms. This condom is a thin sheath that covers the penis to collect sperm and prevent it from entering the woman's body. Female condoms. These are thin, flexible plastic pouches. A portion of the condom is inserted into a woman's vagina before intercourse to prevent sperm from entering the uterus. Contraceptive sponges. These are soft, disposable, spermicide-filled foam sponges. One is inserted into the vagina before intercourse.8 The sponge helps block sperm from entering the uterus, and the spermicide also kills the sperm cells. Spermicides. A spermicide can kill sperm cells. A spermicide can be used alone or in combination with a diaphragm or cervical cap. Diaphragms. Each diaphragm is a shallow, flexible cup made of latex or soft rubber that is inserted into the vagina before intercourse, blocking sperm from entering the uterus. Spermicidal cream or jelly should be used with a diaphragm. Cervical caps. These are similar to diaphragms but are smaller and more rigid. The cervical cap is a thin silicone cup that is inserted into the vagina before intercourse to block sperm from entering the uterus. As with a diaphragm, the cervical cap should be used with spermicidal cream or jelly.
A sterilization implant is a nonsurgical method for permanently blocking the fallopian (pronounced fuh-LOH-pee-uhn) tubes.11 A health care provider threads a thin tube through the vagina and into the uterus to place a soft, flexible insert into each fallopian tube. No incisions are necessary. During the next 3 months, scar tissue forms around the inserts and blocks the fallopian tubes so that sperm cannot reach an egg. After 3 months, a health care provider conducts tests to ensure that scar tissue has fully blocked the fallopian tubes. A backup method of contraception is used until the tests show that the tubes are fully blocked.
Tubal ligation (pronounced TOO-buhl lahy-GEY-shuhn) is a surgical procedure in which a doctor cuts, ties, or seals the fallopian tubes. This procedure blocks the path between the ovaries and the uterus. The sperm cannot reach the egg to fertilize it, and the egg cannot reach the uterus.12
Vasectomy (va-SEK-tuh-mee) is a surgical procedure that cuts, closes, or blocks the vas deferens (pronounced vas DEF-uh-renz). This procedure blocks the path between the testes and the urethra (yoo-REE-thruh).13 The sperm cannot leave the testes and cannot reach the egg. It can take as long as 3 months for the procedure to be fully effective. A backup method of contraception is used until tests confirm that there is no sperm in the semen.
Copper IUD. The copper IUD is the most effective method of emergency contraception. The device can be inserted within 120 hours of unprotected intercourse. The method is nearly 100% effective at preventing pregnancy and has the added benefit of providing a highly effective method of contraception for as long as the device remains in place. There are very few contraindications to use of the copper IUD, and there are no issues related to weight or obesity associated with the effectiveness of the method.
Emergency contraceptive pills (ECPs) are hormonal pills, taken either as a single dose or two doses 12 hours apart, that are intended for use in the event of unprotected intercourse. If taken prior to ovulation, the pills can delay or inhibit ovulation for at least 5 days to allow the sperm to become inactive. They also cause thickening of cervical mucus and may interfere with sperm function. ECPs should be taken as soon as possible after semen exposure and should not be used as a regular contraceptive method. Pregnancy can occur if the pills are taken after ovulation or if the woman has unprotected sex in the same cycle.