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). Estrogen and progesterone help prepare the body for possible fertilization (see Luteal phase). 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 21 to 24 days, not taken for a week (allowing the menstrual period to occur), then started again. Inactive (placebo) tablets may be included for the week when combination tablets are not taken to establish a routine of taking one tablet a day. The inactive tablet may contain iron and folate. Iron is included to help prevent or treat iron deficiency because iron is lost in menstrual blood each month. Folate is included in case women, who may unknowingly have a folate deficiency, become pregnant. Folate deficiency in a pregnant woman increases the risk of birth defects such as spina bifida.
Other combination contraceptives have different schedules. 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 (no menstrual periods), but irregular bleeding is more likely to 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 (10 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 until menopause.
Progestin-only tablets are taken every day of the month at the same time of day. They often cause irregular bleeding. Pregnancy rates may be slightly higher with these tablets than with combination tablets. Progestin-only tablets are usually prescribed only when taking estrogen may be harmful. For example, these tablets may be used by women who have migraines with an aura (symptoms that occur before the headache), high blood pressure, or diabetes.
Before starting oral contraceptives, a woman must see a doctor. Doctors ask the woman about her medical, social, and family history to determine whether she has any health problems that would make taking these contraceptives risky for her. They measure her blood pressure. If it is high, combination oral contraceptives (estrogen plus a progestin) should not be prescribed. A pregnancy test is done to rule out pregnancy. Doctors also often do a physical examination, although this examination is not necessary before a woman starts taking oral contraceptives. 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 once a year.
Women can start taking oral contraceptives at any time of month. However, they should use a backup contraceptive method for the first month. Women who have just had a miscarriage or an abortion during the 1st or 2nd trimester of pregnancy should start using contraception immediately because release of an egg (ovulation) may occur within 7 to 10 days. Those who have just had a full-term baby should wait 21 days. If they are breastfeeding or have risk factors for blood clots (such as being obese or having had a cesarean delivery), they should wait 42 days. Blood clots are more likely to develop during pregnancy and after delivery. Taking combination oral contraceptives also makes blood clots more likely to develop.
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. Women with diabetes can usually take combination oral contraceptives unless diabetes has damaged blood vessels or they have had diabetes for more than 20 years.
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 dysphoric disorder (the severe form of premenstrual syndrome), irregular bleeding, iron deficiency anemia, noncancerous (benign) breast disorders, ovarian cysts, mislocated (ectopic) pregnancies (almost always in the fallopian tubes), and infections of the fallopian tubes. Women who have taken oral contraceptives are less likely to develop osteoporosis.
Taking oral contraceptives reduces the risk of developing cancer of the uterus (endometrial cancer) and cancer of the ovaries. The risk is reduced for at least 20 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.
The disadvantages may include bothersome side effects. Irregular bleeding is common during the first few months of oral contraceptive use, particularly if women forget to take the tablets, but it usually stops as the body adjusts to the hormones. If irregular bleeding persists, doctors may increase the dose of estrogen.
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. 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.
Oral contraceptives can also cause vomiting, headaches, depression, and problems sleeping.
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 twice as high for women who take combination oral contraceptives as for those who do not. 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 being immobilized for a long time also increases the risk of developing blood clots, women should stop taking oral contraceptives a month before major elective surgery and not take them again until a month afterward. If surgery requires only minimal immobilization (as for minor outpatient surgery or laparoscopic surgery), stopping oral contraceptives is not necessary.
Women who use oral contraceptives, particularly for more than 5 years, are slightly more likely to develop cervical cancer. But 10 years after stopping use, this risk decreases to what it was before starting oral contraceptives. Also, whether the increased risk is related to the oral contraceptives is unclear. Women who are taking oral contraceptives should have Papanicolaou (Pap) tests as recommended in by their doctor (see Screening for Cervical Cancer). Such tests can detect precancerous changes in the cervix early—before they lead to cancer.
Taking low-dose oral contraceptives does not cause gallstones to form.
If women developed jaundice due to reduced or slow movement of bile through the bile ducts (cholestasis) during a previous pregnancy, they may have the same problem when they take oral contraceptives. They may still be able to take oral contraceptives, but they should have regular examinations and blood tests to check for this problem. However, if women developed jaundice when they took oral contraceptives in the past, they should not take them again.
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.
If women have a high triglyceride (a fat) level, taking combination oral contraceptives can increase the level even more. A high triglyceride level may increase the risk of a heart attack or stroke in people who have other risk factors for these disorders. Oral contraceptives increase the risk of blood clots (which can also contribute to heart attacks and strokes). So, women with a high triglyceride level should not take combination oral contraceptives.
Taking certain drugs can make oral contraceptives less effective. These drugs include some anticonvulsants (mainly phenytoin, carbamazepine, primidone, topiramate, and oxcarbazepine), a certain combination of drugs used to treat human immunodeficiency virus (HIV) infection (ritonavir plus another protease inhibitor), and the antibiotics rifampin and rifabutin. If women taking oral contraceptives have to take one of these drugs, they should also use another contraceptive method while they are taking the drug, and they should continue using another contraceptive method until their first period occurs after they stop the drug. Women should not take lamotrigine (an anticonvulsant) with oral contraceptives. Oral contraceptives may make lamotrigine less effective in controlling seizures.
*These prohibitions apply only to oral contraceptives that contain estrogen and a progestin.
mg/dL = milligrams per deciliter of blood.
Oral contraceptives do not increase the risk of breast cancer in women who are currently taking them, in women aged 35 to 65 who used to take them, or in women who have certain benign breast disorders or a family history of breast cancer.
For healthy women who do not smoke, taking low-dose combination tablets with a low dose of estrogen does not increase the risk of having a stroke or heart attack.
Skin Patches and Vaginal Rings
Skin patches and vaginal rings contain estrogen and a progestin. They should be used for 3 weeks, then not used for 1 week to allow the menstrual period to occur. Or they may be used continuously. In such cases, periods do not occur. Depending on when women start using the patch or ring, they may have to use a backup method of birth control during the first week that they use the patch or ring.
A contraceptive skin patch is attached to the skin with an adhesive. It should be left in place for 1 week, then removed and replaced with a new patch, which is placed on a different area of the skin. A new patch is applied once a week (on the same day each week) for 3 weeks, followed by a week when no patch is used. Exercise and use of saunas or hot tubs do not displace the patch. Skin under and around the patch may become irritated.
A vaginal ring is a small plastic device that is placed in the vagina. It should be left in place for 3 weeks, then removed for 1 week. Or the ring may be left in place for 4 or even 5 weeks, then removed and replaced with a new ring. A new ring is used each time. 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. The ring does not dissolve and cannot be pushed too far up.
Either method is effective. About 0.3% of women who use one of these methods as instructed become pregnant during the first year of use. Effectiveness is similar to that of oral contraceptives. The patch may be less effective in overweight women.
If women use a patch or a ring for 3 weeks (replacing it each week), followed by 1 week when no patch or ring is used, they typically have a regular menstrual period. Spotting or bleeding between periods (breakthrough bleeding) is uncommon. However, if women use a patch or ring continuously, irregular bleeding becomes more common the longer they use this method.
Side effects, effects on the risk of developing disorders, and restrictions on use are similar to those of combination oral contraceptives.
A contraceptive implant is a single match-sized rod containing a progestin. The implant releases the progestin slowly into the bloodstream. The type of implant available in the United States is effective for 3 years.
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 incision or stitches are necessary. Doctors must receive special training before they can do this procedure.
If women have not had unprotected sex since their last period, an implant can be inserted at any time during the menstrual cycle. If women have had unprotected sex, they should use another form of contraception until their next menstrual period. Then a pregnancy test is done to rule out pregnancy. If women are not pregnant, the implant can be inserted. An implant can also be inserted immediately after a miscarriage, an abortion, or delivery of a baby.
The most common side effect is irregular or no menstrual periods. Women may also have headaches. 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.
An injection may be given immediately after a miscarriage, an abortion, or delivery of a baby. If the interval between injections is more than 4 months, a pregnancy test is done to rule out pregnancy before the injection is given.
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 the women within 6 months and in about three fourths within 1 year. Fertility may not return for up to 18 months after injections are stopped.
Women typically gain 3 to 9 pounds during the first year of use and continue to gain weight. To prevent this gain, women need to limit calories and increase the amount of exercise they do. Headaches are common, but they usually become less severe over time. If women have had tension headaches and migraines in the past, the injections do not make them worse. Bone density temporarily decreases. However, the risk of fractures does not increase, and bones usually return to their previous density after the injections are stopped. Taking calcium and vitamin D supplements daily to help maintain bone density is important for all women, but it is particularly important for adolescent and young women who are getting progestin injections.
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. Unlike combination oral contraceptives, progestin injections do not increase the risk of high blood pressure or blood clots.
Last full review/revision August 2013 by Laura Sech; Daniel R. Mishell, Jr., MD; Emily Silverstein