Contraception is prevention of fertilization of an egg by a sperm (conception) or attachment of the fertilized egg to the lining of the uterus (implantation).
There are several methods of contraception. None is completely effective, but some methods are far more reliable than others. Effectiveness often depends on how closely people follow instructions. Following instructions for some methods is easier than for others. Thus, the difference in effectiveness between typical use (which is often inconsistent) and perfect use (following the instructions exactly) may vary greatly from one method to another. For example, oral contraceptives are very effective with perfect use. However, many women forget to take some doses. Thus, average use of oral contraceptives is much less effective than perfect use. In contrast, contraceptive implants, once inserted, require nothing more (and are thus used perfectly) until they need to be replaced. Thus, typical use is the same as perfect use (until implants need to be replaced). People tend to follow instructions more closely as they get used to using a method. As a result, the difference between effectiveness with perfect use and that with typical use often decreases as time passes.
Besides its degree of effectiveness, each contraceptive method has other advantages and disadvantages. For example, hormonal methods have certain side effects and increase or decrease women's risk of developing certain disorders. Choice of method depends on lifestyle, preferences, and the degree of reliability needed.
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Contraceptive hormones can be taken by mouth, inserted into the vagina, applied to the skin, implanted under the skin, or injected into muscle. The hormones used to prevent conception include estrogen and progestins (drugs similar to the hormone progesterone). Hormonal methods prevent pregnancy mainly by stopping the ovaries from releasing eggs or by keeping mucus in the cervix thick so that sperm cannot pass through the cervix into the uterus. Thus, hormonal methods prevent the egg from being fertilized.
All hormonal methods can have similar side effects and restrictions on use.
Oral contraceptives, commonly known as birth control pills or just “the pill,” contain hormones—either a combination of a progestin and estrogen or a progestin alone.
Combination tablets are typically taken once a day for 3 weeks, not taken for a week (allowing the menstrual period to occur), then started again. Inactive tablets may be included for the week when combination tablets are not taken to establish a routine of taking one tablet a day. One product is taken daily for 12 weeks, then not taken for 1 week. Thus, menstrual periods occur only 4 times a year. Another product involves taking an active tablet every day. With this product, there is no scheduled bleeding episode, but unscheduled bleeding episodes often occur. About 0.3% of women who take combination tablets as instructed become pregnant during the first year of use. However, the chances of becoming pregnant increase substantially if women skip or forget to take a tablet, especially the first ones in a monthly cycle.
The dose of estrogen in combination tablets varies. Usually, combination tablets with a low dose of estrogen (20 to 35 micrograms) are used because they have fewer serious side effects than those with a high dose (50 micrograms). Healthy women who do not smoke can take low-dose combination tablets without interruption until menopause.
Progestin-only tablets are taken every day of the month. They often cause irregular bleeding. Pregnancy rates are about the same as those with combination tablets. Progestin-only tablets are usually prescribed only when taking estrogen may be harmful. For example, these tablets may be prescribed for women who are breastfeeding because estrogen reduces the amount and quality of breast milk produced. Progestin-only tablets do not affect breast milk production.
Before starting oral contraceptives, a woman should have a physical examination, including measurement of blood pressure, to make sure she has no health problems that would make taking the contraceptives risky for her. Three months after starting oral contraceptives, the woman should have another examination to determine whether her blood pressure has changed. If it has not, she should then have an examination at least once a year.
If a woman has coronary artery disease or diabetes or has risk factors for them (such as a close relative with either disorder), a blood test is usually done to measure levels of cholesterol, other fats (lipids), and sugar (glucose). Even if these levels are abnormal, doctors may still prescribe a low-dose estrogen combination contraceptive. However, they periodically do blood tests to monitor the woman's lipid and sugar levels.
Also before starting oral contraceptives, a woman should talk with her doctor about the advantages and disadvantages of oral contraceptives for her situation.
The main advantage is reliable, continuous contraception if oral contraceptives are taken as instructed. Also, taking oral contraceptives reduces the occurrence of menstrual cramps, premenstrual syndrome, acne, irregular bleeding, iron deficiency anemia, breast cysts, ovarian cysts, mislocated (ectopic) pregnancies (almost always in the fallopian tubes), and infections of the fallopian tubes. Also, women who have taken oral contraceptives are less likely to develop osteoporosis.
Taking oral contraceptives reduces the risk of developing several types of cancer, including uterine (endometrial) and ovarian. The risk is reduced for many years after the contraceptives are stopped.
Oral contraceptives taken early in a pregnancy do not harm the fetus. However, they should be stopped as soon as the woman realizes she is pregnant. Oral contraceptives do not have any long-term effects on fertility, although a woman may not release an egg (ovulate) for a few months after stopping the drugs. Doctors recommend that women wait 2 weeks after delivery before they start taking oral contraceptives.
The disadvantages may include bothersome side effects. Irregular bleeding is common during the first few months of oral contraceptive use but usually stops as the body adjusts to the hormones. If irregular bleeding persists, doctors may suggest taking oral contraceptives every day, without any breaks, for several months to reduce the number of bleeding episodes.
Some side effects are related to the estrogen in the tablet. They may include nausea, bloating, fluid retention, an increase in blood pressure, breast tenderness, and migraine headaches. Others are related mostly to the type or dose of the progestin. They may include weight gain, acne, and nervousness. Some women who take oral contraceptives gain 3 to 5 pounds because of fluid retention. They may gain even more because appetite also increases. Many of these side effects are uncommon with the low-dose tablets.
In some women, oral contraceptives cause dark patches (melasma) on the face, similar to those that may occur during pregnancy. Exposure to the sun darkens the patches even more. If dark patches develop, women should discuss stopping the oral contraceptives with their doctor. The patches slowly fade after the contraceptives are stopped.
Taking oral contraceptives increases the risk of developing some disorders. The risk of developing blood clots in veins is higher for women who take combination oral contraceptives than for those who do not. The risk is 7 times higher with tablets containing a high dose of estrogen and 3 to 4 times higher with tablets containing a low dose of estrogen. However, this risk is still only half the risk of developing blood clots during pregnancy. Women with family members who have had blood clots should inform their doctor before taking oral contraceptives. Because surgery also increases the risk of developing blood clots, women must stop taking oral contraceptives a month before major elective surgery and not take them again until a month afterward. For healthy women who do not smoke, taking combination tablets with a low dose of estrogen does not increase the risk of having a stroke or heart attack.
Use of oral contraceptives, particularly for more than 5 years, may increase the risk of developing cervical cancer. Women who are taking oral contraceptives should have a Papanicolaou (Pap) test at least once a year. Such tests can detect precancerous changes in the cervix early—before they lead to cancer.
The current use of oral contraceptives does not increase overall risk of breast cancer, nor does former use in women aged 35 to 65. Also, use does not further increase breast cancer risk in high-risk groups (for example, women with certain benign breast disorders or a family history of breast cancer).
Taking oral contraceptives causes existing gallstones to grow faster but does not cause new stones to form. Thus, gallstones are diagnosed more often during the first few years of oral contraceptive use.
For women who are older than 35 and who smoke, using oral contraceptives increases their risk of having a heart attack. Typically, such women should not use oral contraceptives. However, if they are closely monitored by a health care practitioner, some of them may be able to take oral contraceptives.
Taking cyclophosphamide, certain antibiotics, or possibly certain antifungal drugs can make oral contraceptives less effective. If women taking oral contraceptives take one of these drugs, they should also use another contraceptive method until the beginning of their first period after stopping the drug.
*These restrictions apply only to oral contraceptives that contain estrogen and a progestin.
mg/dL = milligrams per deciliter of blood.
Skin Patches and Vaginal Rings
Skin patches and vaginal rings that contain estrogen and a progestin are used for 3 of 4 weeks, then removed. In the 4th week, no contraception is used to allow the menstrual period to occur.
A contraceptive skin patch is placed on the skin once a week for 3 weeks. The patch is left in place for 1 week, then removed, and a new patch is placed on a different area of the skin. During the 4th week, no patch is used. Exercise and use of saunas or hot tubs do not displace the patches.
A vaginal ring is a small plastic device that is placed in the vagina and left there for 3 weeks. Then it is removed for 1 week. A woman can place and remove the vaginal ring herself. The ring comes in one size and can be placed anywhere in the vagina. Usually, the ring is not felt by the woman's partner during intercourse. A new ring is used each month.
Either method is effective, particularly with perfect use. Effectiveness is similar to that of oral contraceptives. Sometimes the patch is less effective in overweight women.
With either method, a woman has a regular menstrual period. Spotting or bleeding between periods (breakthrough bleeding) is uncommon. Side effects, effects on the risk of developing disorders, and restrictions on use are similar to those of combination oral contraceptives.
Contraceptive implants are a single rod containing a progestin. After numbing the skin with an anesthetic, a doctor uses a needle-like instrument (trocar) to place the implant under the skin of the inner arm above the elbow. No stitches are necessary. The implants release the progestin slowly into the bloodstream. The type of implant available in the United States is effective for 3 years.
The most common side effect is irregular or no menstrual periods during the first year of use. After that, periods frequently become regular. Headaches and weight gain may also occur. These side effects prompt some women to have the implant removed. Because the implant does not dissolve in the body, a doctor has to make an incision in the skin to remove it. Removal is more difficult than insertion because tissue under the skin thickens around the implant. As soon as the implant is removed, the ovaries return to their normal functioning, and women become fertile again.
A progestin called medroxyprogesterone acetate is injected by a health care practitioner once every 3 months. Two types of injections are available. One is injected into a muscle of the arm or buttock. The other is injected under the skin. Each type is very effective.
The progestin completely disrupts the menstrual cycle. About one third of women using this contraceptive have no menstrual bleeding during the 3 months after the first injection, and another third have irregular bleeding and spotting for more than 11 days each month. After this contraceptive is used for a while, irregular bleeding occurs less often. After 2 years, about 70% of the women have no bleeding at all. When the injections are stopped, a regular menstrual cycle resumes in about half of the women within 6 months and in about three fourths within 1 year. Fertility may not return for up to a year after injections are stopped.
Common side effects include a slight weight gain, headache, irregular or no menstrual periods, and a temporary decrease in bone density. Bones usually return to their previous density after the injections are stopped. People getting injections, particularly teenagers and young women, should take calcium and vitamin D supplements daily to help maintain bone density.
Medroxyprogesterone acetate does not increase the risk of developing any cancer, including breast cancer. It reduces the risk of developing uterine (endometrial) cancer, pelvic inflammatory disease (an infection of the upper female reproductive organs), and iron deficiency anemia. Interactions with other drugs are uncommon.
Emergency contraception, the so-called morning-after pill, consists of synthetic hormones or drugs that affect hormones. It is used within 72 hours after one act of unprotected sexual intercourse or after one occasion when a contraceptive method fails (for example, when a condom breaks).
Emergency contraception decreases the chance of pregnancy after one act of unprotected intercourse, including when the act occurs near the time the egg is released (ovulation)—when conception is most likely. Near ovulation, the chance of pregnancy is about 8% without contraception. The sooner emergency contraception is taken, the more likely it is to be effective.
Two options are available:
Barrier contraceptives physically block the sperm's access to a woman's uterus. They include the condom, diaphragm, cervical cap, and contraceptive sponge.
Condoms are thin protective sheaths that cover the penis. Condoms made of latex are the only contraceptives that provide protection against all common sexually transmitted diseases, including those due to bacteria (such as gonorrhea and syphilis) and those due to viruses (such as HPV—human papillomavirus—and HIV—human immunodeficiency virus). However, this protection, though considerable, is not complete. Condoms made of polyurethane also provide protection, but they are thinner and more likely to tear. Condoms made of lambskin do not protect against viral infections such as HIV infection.
Condoms must be used correctly to be effective (see Sexually Transmitted Diseases: How to Use a Condom). With some condoms, the tip needs to be positioned so that it extends about ½ inch (about 1¼ centimeters) beyond the penis to provide a space to collect semen. Other condoms have a reservoir at the tip for this purpose. Immediately after ejaculation, the penis should be withdrawn while the condom's rim is held firmly against the base of the penis to prevent the condom from slipping off and spilling semen. The condom should then be removed carefully. If semen is spilled, sperm could enter the vagina, resulting in pregnancy. A new condom should be used each time a person has sexual intercourse, and the condom should be discarded if its integrity is in doubt.
During the first year condoms are used, the chance of pregnancy is about 6% with perfect use and about 16% with typical use. A substance that kills sperm (spermicide), which may be included in the condom's lubricant or inserted separately into the vagina, increases the effectiveness of condoms.
The diaphragm, a dome-shaped rubber cup with a flexible rim, is inserted into the vagina and positioned over the cervix. A diaphragm prevents sperm from entering the uterus.
Diaphragms come in various sizes and must be fitted by a health care practitioner, who also teaches the woman how to insert it. If a woman has gained or lost more than 10 pounds, has had a diaphragm for more than a year, or has had a baby or an abortion, she must be refitted for a diaphragm because the vagina's size and shape may have changed.
A diaphragm should cover the entire cervix without causing discomfort. Neither the woman nor her partner should notice its presence. A contraceptive cream or jelly (which kills sperm) should always be used with a diaphragm, in case the diaphragm is displaced during intercourse. The diaphragm is inserted before intercourse and should remain in place for at least 8 hours but no more than 24 hours afterward. If sexual intercourse is repeated while the diaphragm is in place, additional contraceptive cream or jelly should be inserted into the vagina to continue protection. A woman should inspect the diaphragm regularly for tears.
During the first year of diaphragm use, the percentage of women who become pregnant is about 6% with perfect use and about 16% with typical use.
The cervical cap resembles the diaphragm but is smaller and more rigid. It fits snugly over the cervix. It is not available in the United States.
Cervical caps must be fitted by a health care practitioner. A contraceptive cream or jelly should always be used with a cervical cap. The cap is inserted before intercourse and left in place for at least 8 hours after intercourse, up to 48 hours at a time.
During the first year of use by women who have not had children, pregnancy occurs in about 9% with perfect use and about 18% with typical use. About twice as many women who have had children become pregnant. Childbirth changes the cervix, making it more difficult to securely fit with a cap.
In addition to blocking sperm from entering the uterus, the sponge contains a spermicide. It is available over the counter and does not need to be fitted by a health care practitioner.
The sponge can be inserted into the vagina by the woman up to 24 hours before sexual intercourse and provides protection through that period of time, regardless of how frequently intercourse is repeated. The sponge must be left in place for at least 6 hours after the last act of intercourse. It should not be left in place for more than 30 hours. Usually, neither partner is aware of its presence once it is inserted. It is less effective than the diaphragm.
Problems related to use are uncommon. They include allergic reactions, vaginal dryness or irritation, and difficulty removing the sponge.
Spermicides are preparations that kill sperm on contact. They are available as vaginal foams, creams, gels, and suppositories and are placed in the vagina before sexual intercourse. These contraceptives also provide a physical barrier to sperm. No single type of preparation is more effective than another. Spermicides are best used with a barrier contraceptive, such as a condom or diaphragm.
Intrauterine devices (IUDs) are small, flexible plastic devices that are inserted into the uterus. An IUD is left in place for 5 or 10 years, depending on the type, or until the woman wants the device removed. IUDs must be inserted and removed by a doctor or other health care practitioner. Insertion takes only a few minutes. Removal is also quick and usually causes minimal discomfort. IUDs prevent pregnancy in many ways:
Two types of IUDs are currently available in the United States. One type, which releases a progestin (levonorgestrel), is effective for 5 years. During that time, only about 0.5% of women become pregnant. The other type, which releases copper, is effective for at least 10 years. During that time, less than 2% of women become pregnant. One year after removal of an IUD, 80 to 90% of women who try to conceive do so.
An IUD inserted up to 1 week after one act of unprotected sexual intercourse is nearly 100% effective as a method of emergency contraception. IUDs do not have any general, bodywide (systemic) effects.
The uterus is briefly contaminated with bacteria at the time of insertion, but an infection rarely results. IUD strings do not provide access for bacteria. An IUD increases the risk of a pelvic infection only during the first month of use.
Bleeding and pain are the main reasons that women have an IUD removed, accounting for more than half of all removals before the usual replacement time. The copper-releasing IUD increases the amount of menstrual bleeding. In contrast, the progestin-releasing IUD reduces the amount, and after 1 year, menstrual bleeding stops completely in about 20% of women.
About 5% of IUDs are expelled during the first year after insertion, often during the first few weeks. Sometimes a woman does not notice the expulsion. A plastic string is attached to the IUD so that a woman can check every so often, especially after a menstrual period, to make sure that the IUD is still in place. If she cannot find the string, she should use another contraceptive method until she can see her health care practitioner to determine whether the IUD is still in place. If another IUD is inserted after one has been expelled, it usually stays in place.
Rarely, the uterus is perforated during insertion. Usually, perforation does not cause symptoms. It is discovered when a woman cannot find the plastic string and ultrasonography or an x-ray shows the IUD located outside the uterus. An IUD that perforates the uterus and passes into the abdominal cavity must be surgically removed, sometimes using laparoscopy, to prevent it from injuring and scarring the intestine.
The risk of miscarriage is about 55% in women who become pregnant with an IUD in place. If a woman wishes to continue the pregnancy and the string of the IUD is visible, a doctor removes the IUD to reduce the risk of miscarriage (to about 20%). Becoming pregnant with an IUD in place does not increase the risk of birth defects, death of the fetus, or pelvic infection during pregnancy. For women who conceive with an IUD in place, the likelihood of having a mislocated (ectopic) pregnancy is about 5%. Nonetheless, the overall risk of an ectopic pregnancy is much lower for women using IUDs than for those not using a contraceptive method because IUDs prevent pregnancy effectively.
In addition to providing effective birth control, IUDs may reduce the risk of uterine (endometrial) and cervical cancer.
Some contraceptive methods depend on the timing of intercourse rather than on drugs or devices.
Natural Family Planning Methods
Natural family planning (rhythm) methods depend on abstinence from sexual intercourse during the woman's fertile time of the month. In most women, the ovary releases an egg about 14 days before the start of a menstrual period. Although the unfertilized egg survives only about 12 hours, sperm can survive for as long as 5 days after intercourse. Consequently, fertilization can result from intercourse that occurred up to 5 days before and 12 hours after the release of the egg.
There are several methods of natural family planning. Each method tries to estimate when the egg is released (ovulation). The calendar method is the least effective method. The temperature, mucus, and symptothermal methods more accurately estimate when ovulation occurs.
This method is particularly ineffective for women who have irregular menstrual cycles. To calculate when to abstain from intercourse, a woman subtracts 18 days from the shortest and 11 days from the longest of her previous 12 menstrual cycles. For example, if cycles last from 26 to 29 days, she must abstain from intercourse from day 8 (26 minus 18) through day 18 (29 minus 11) of each cycle. The more the cycle length varies, the longer a woman must abstain. The day that a menstrual period begins is considered day 1.
A woman's body temperature at rest (basal body temperature) increases slightly, by about 0.9° F (0.5° C), after the egg is released. To determine her basal body temperature, the woman takes her temperature each morning before she gets out of bed. If possible, she should use a basal body temperature thermometer (which is highly accurate) or, if unavailable, a mercury thermometer. Electronic thermometers are the least accurate.
The temperature should be recorded each day. The woman abstains from intercourse from the time her menstrual period begins until at least 72 hours after the day her basal body temperature increased.
The woman determines her fertile period by observing secretions (cervical mucus) from the vagina, if possible, several times every day, starting the day after a menstrual period stops. There may be no mucus for a few days after the period stops, but then it appears and is cloudy and thick. Shortly before ovulation, more mucus is produced, and the mucus becomes thinner, elastic (stretching between the fingers), clearer, and more watery (like a raw egg white). Observations should be recorded.
Intercourse is permitted when mucus is absent but is restricted to every other day during this time because semen may be confused with mucus. Once mucus appears, intercourse is avoided until 3 or 4 days after the changes in mucus indicate ovulation. Intercourse is then permitted without restrictions on how often until the next period begins. Women who use this method should not use douches or feminine hygiene sprays and creams because these products can change the mucus.
Women who use this method should not use douches or feminine hygiene sprays and creams because these products can change the mucus.
This method combines the temperature, mucus, and calendar methods. The woman notes when cervical mucus increases in amount and becomes thinner, elastic, clearer, and more watery (as for the mucus method) and when temperature increases. She should abstain from intercourse from the first day requiring abstinence according to the calendar method until at least 72 hours after the day her basal body temperature increases (as for the temperature method) and cervical mucus changes.
Of the natural family planning methods, this one is the most reliable. With perfect use, the chance of pregnancy is about 2% per year.
|All in the Timing: Natural Family Planning
Natural family planning involves abstaining from sexual intercourse when the woman may be fertile. Days to abstain may be based only on the timing of the menstrual period (calendar method), on the woman's temperature, on characteristics of cervical mucus (which change during the month), or on a combination of these methods (symptothermal method).
The exact days of abstinence vary from woman to woman because the length of a woman's cycle, the day her temperature increases, the pattern of changes in mucus, and the timing of other symptoms vary. The chart shown below gives only a general idea of how family planning methods are used. Having irregular menstrual periods makes using natural family planning methods more uncertain.
For the calendar method in the example below, 18 days were subtracted from the shortest cycle (26 – 18 = 8) and 11 days were subtracted from the longest (29 – 11 = 18). So the woman abstains from intercourse from day 8 through day 18.
For the temperature method, the woman abstains from intercourse from the beginning of her menstrual period until at least 72 hours after the day her basal body temperature increased.
For the mucus method, the woman abstains from intercourse during her menstrual period and from the time that cervical mucus appears until 4 days after she observes the largest amount of mucus and it becomes thinner, elastic, clearer, and more watery. She can have intercourse between the end of her menstrual period and the time mucus appears. But during this time, she should limit sexual intercourse to every other day so that she does not confuse semen with mucus from the cervix.
For the symptothermal method, the woman uses the temperature, mucus, and calendar methods. The woman notes when cervical mucus increases and changes in appearance and when basal body temperature increases. She abstains from intercourse starting the same day as determined by the calendar method until at least 72 hours after the day her temperature increases and the mucus changes, indicating ovulation.
Withdrawal Before Ejaculation
To prevent sperm from entering the vagina, a man can withdraw the penis from the vagina before ejaculation, when sperm are released during orgasm. This method, also called coitus interruptus, is not reliable because sperm may be released before orgasm. It also requires that the man have a high degree of self-control and precise timing.
Last full review/revision August 2007 by Daniel R. Mishell, Jr., MD