- Introduction to birth control
- Types of hormonal methods of contraception
- What are advantages and disadvantages of hormonal birth control methods?
- Oral hormones: The pill
- What are the side effects of the pill?
- How is the pill taken?
- How long will it take before the pill prevents conception?
- What drugs or conditions reduce the effectiveness of the pill?
- What are the benefits of taking the pill?
- When will I start having periods again after I quit taking the pill?
- Injection: depot medroxyprogesterone acetate (DMPA)
- Contraceptive patch: Ortho-Evra
- Contraceptive implants
- Vaginal ring: NuvaRing
- How effective are hormonal birth control methods?
Introduction to birth control
If a woman is sexually active and she is fertile, meaning that she is physically able to become pregnant, she needs to ask herself, "Do I want to become pregnant now?" If her answer is "No," she must use some method of birth control (contraception).
Terminology for "birth control" includes contraception, pregnancy prevention, fertility control, and family planning. But no matter what the terminology, sexually active people can choose from a variety of methods to reduce the possibility of their becoming pregnant. Nevertheless, no method of birth control available today offers perfect protection against sexually transmitted infections (sexually transmitted diseases, or STDs), except abstinence.
In simple terms, all methods of birth control are based on either preventing a man's sperm from reaching and entering a woman's egg (fertilization) or preventing the fertilized egg from implanting in the woman's uterus (her womb) and starting to grow. New methods of birth control are being developed and tested. And what is appropriate for a couple at one point may change with time and circumstances.
Unfortunately, no birth-control method, except abstinence, is considered to be 100% effective.
Types of hormonal methods of contraception
There are several different hormonal methods of birth control. The differences among them involve
- the type of hormone,
- the amount of hormone, and
- the way the hormone enters a woman's body.
The hormones can be estrogen and/or progesterone, or preparations that contain a combination of these hormones. These hormones may be taken orally (taken by mouth), implanted into body tissue, injected under the skin, absorbed from a patch on the skin, or placed in the vagina. The mode of delivery determines whether the hormonal exposure is continuous or intermittent.
What are advantages and disadvantages of hormonal birth control methods?
Advantages of hormonal methods of birth control include that they are all highly effective and their effects are reversible. They do not rely on spontaneity and can be used in advance of sexual activity.
Disadvantages of hormonal methods for birth control include:
- The necessity of taking medications continuously
- The cost of the medications
- Women must remember to take them regularly or use them exactly as prescribed
- A doctor’s visit and prescription are required.
- They do not protect a woman against STDs or sexually transmitted diseases
- Women must begin using hormonal contraceptives in advance before they become effective.
- For some women, hormonal preparations are associated with unpleasant side effects or increased health risks.
Oral hormones: The pill
The combination pill contains the hormones estrogen and progestin, a form of progesterone. When a woman uses the combination pill, the eggs in her ovaries do not mature and she does not ovulate. She doesn't become pregnant because no egg is available to be fertilized by a sperm.
The traditional combination pill comes in 21-day packs or 28-day packs depending on the manufacturer. The 21-pill pack has pills for 21 "on" days and no pills for the seven "off" days that follow. The 28-pill pack has active pills for the first 21 "on" days and seven inactive (placebo) or reminder pills for the following seven "off" days.
New preparations have been developed that allow for extended or continuous use of combination pills for months at a time. These products allow for a reduction in the number of menstrual periods a woman experiences.
The minipill only contains one hormone, progestin. Progestin thickens the cervical mucus, making it more difficult for sperm to pass through the cervix. It also makes the lining of the uterus less receptive to the implantation of a fertilized egg. The progesterone-only pill is sometimes recommended for women who have medical reasons for which they must avoid taking estrogen hormones. (These reasons can include liver disease, certain types of blood clots in the veins, breast cancer, and uterine cancer.) In addition, it is often recommended in nursing mothers because it has no adverse effects on breastfeeding. Indeed, extended breastfeeding, as well as delay in the need for formula supplementation has been observed in breastfeeding users of the minipill.
How is the minipill taken?
The minipill is taken every day. There are no "on" or "off" days with the minipill.
What are the side effects of the pill?
- Some women experience temporary symptoms of spotting or light vaginal bleeding, breast tenderness, and nausea during the first one to three months of taking the pill. Nausea can be helped if the pill is taken after a meal.
- While women sometimes fear weight gain with oral contraceptives, studies of the low-dose preparations demonstrate that there is no significant weight gain with oral contraception and no major difference in weight change comparing various contraception products.
- Negative mood changes, such as depression, and pigmented patches of skin on the face (melasma) may occur with oral-contraceptive use.
- Because the progesterone in women can cause thinning of the lining of the uterus, some women may experience loss of menstrual periods (amenorrhea). Oral contraceptive-induced amenorrhea happens in about 1% of women in the first year of use. As long as the woman is properly taking her pills, amenorrhea is not harmful and it does not signal any loss of effectiveness of the pills.
Most side effects from the combination pill or the minipill decrease after two to three months of use. It is important to remember that because most side effects of oral contraceptives decrease in the first two to three months of use, women should try to avoid switching pills prior to an adequate trial. Trying to stick with any given product for two to three months may be necessary to really determine whether or not it will be tolerated over time. Switching too early to another brand may only needlessly subject the woman to the possibility of similar side effects starting all over again with the new pill.
A woman who is breastfeeding should not use the combination pill because it can reduce the amount of her breast milk and the concentration of proteins and fat in her breast milk. Additionally, her breast milk will contain traces of the hormones from the pill. However, in contrast to the combination pill, the minipill is routinely used in lactating women.
Blood clots in the legs (DVT) and elsewhere are slightly more frequent with low-dose oral contraceptives, but the risk is very low, and lower than the increased risk of clotting that occurs with pregnancy. Nevertheless, oral contraceptives are not recommended for:
- women with clotting tendencies (such as antiphospholipid antibody syndrome, Leiden Factor 5),
- known coronary heart disease,
- unevaluated breast lumps,
- vaginal bleeding, or
- breast cancer.
Smokers over 35 years of age should not use oral contraceptives, nor should women with a significant liver disorder.
A woman should contact her healthcare professional immediately if she experiences any of these side effects while taking the pill:
- severe headache;
- leg cramps;
- change in vision, including blurred vision, vision loss, or flashing lights;
- abdominal pain;
- chest pain;
- shortness of breath;
- coughing up blood; or
- leg swelling or pain.
How is the pill taken?
No matter which type of birth-control pill a woman uses, she should take it every day at the same time in order to establish a routine. The woman needs to minimize the chance she will forget to take the pill, which is not an uncommon occurrence. This is especially critical in the case of the progestin-only pill (minipill). Forgetting to take the minipill, or taking it at varying times of the day, can significantly impair its effectiveness in contraception. This is due to the low dose of the minipill causing its effects to wear off rapidly if the pill is missed.
How long will it take before the pill prevents conception?
- When a woman begins taking the pill, she may not protected from pregnancy until she has been taking the pill for 10 consecutive days in a row. If a woman forgets to take a pill after she has started, she may be at risk for getting pregnant.
- If she only misses one pill, she should take it as soon as she remembers, even if it means taking two pills in the same day.
- If she misses two pills, she should take both of them as soon as she remembers, plus the pill for that day at her regular time.
- If she misses three pills, she should discontinue use of the pill for four more days to complete one week and then begin taking a new pack of birth control pills, whether she has a menstrual period or not. She must use an alternate form of birth control or abstain from sexual activity during the week that she stops taking her pills.
- If a woman continually forgets to take her pills, perhaps she should consider a different method of birth control.
What drugs or conditions reduce the effectiveness of the pill?
- The pill may partially lose its effectiveness if a woman vomits or has diarrhea for any reason.
- Some medications, including certain sedatives and some antibiotics such as penicillin and tetracycline, may reduce the effectiveness of the pill. Research in this area is ongoing.
A woman should ask her healthcare professional about these matters and the necessity of using a backup method of birth control if any of these conditions exist.
What are the benefits of taking the pill?
There are a number of benefits to taking the pill. Both the combination pill and the minipill can regularize a woman's menstrual cycle and reduce her menstrual flow and menstrual cramps. There is evidence that the pill protects against cancer of the ovary and uterus as well as pelvic inflammatory disease (PID) and iron deficiency anemia.
The combination pill can reduce:
- acne (although maximal acne reduction may take six months to occur),
- the risk of an ectopic pregnancy,
- noncancerous breast cysts, and
- ovarian cysts.
According to several studies, the combination pill confers no long-term risk of breast cancer for women at average risk. In addition, a woman who has taken the pill is less likely to develop rheumatoid arthritis and osteoporosis.
Users of oral contraceptives have experienced significant decreases in excessive menstrual flow and in occurrence and severity of menstrual cramps.
When will I start having periods again after I quit taking the pill?
- A woman's menstrual periods should begin again within about 3 months of stopping the oral-contraceptive pill. However, the length of delay before a woman's period returns after stopping the pill varies from woman to woman.
- Oral contraceptives are about 97% effective in preventing pregnancy. The pill does not protect a woman against sexually transmitted infections.
Injection: depot medroxyprogesterone acetate (DMPA)
Depot medroxyprogesterone acetate (DMPA) is a synthetic long-acting form of the hormone progesterone. DMPA is similar to the birth-control minipill in that it does not contain estrogen. Like other progesterone-based contraceptives, DMPA acts by preventing the release of the egg from the ovary (ovulation) and by promoting thick cervical mucus that impedes the sperm's progress. Its effectiveness in preventing pregnancy is close to 100%.
DMPA must be injected by a health-care professional every three months (12 weeks). It is administered as a deep muscle (intramuscular) injection. A lower-dose formulation of the drug that is injected beneath the skin (subcutaneously) is also available. The injection must be administered within the first five days of a woman's menstrual period. She is then protected from pregnancy within 24 hours of receiving the injection.
A woman may stop having periods altogether after using DMPA for one year. After two years of use, 70% of women will have no menstrual bleeding. Menstrual periods stop because the DMPA causes the ovaries to go into a "resting" state. When the ovaries do not release an egg every month, the regular growth of the lining of the uterus does not occur and no uterine lining is shed during the subsequent menstrual cycle.
A woman's menstrual periods should begin again within six to 18 months after she stops taking the injections. A woman can also become pregnant, usually within 12 to 18 months, once she stops using DMPA. If a new mother does not breastfeed her baby, she can resume the injections right after childbirth. Mothers who are breastfeeding can safely begin the injections six weeks after childbirth. The injections do not reduce the flow of her breast milk, and no harmful effects on the baby have been noted.
The most common side effects of DMPA injections are irregular menstrual cycles, cessation of menstrual periods, and weight gain. Other side effects may include nervousness, dizziness, stomach discomfort, headaches, fatigue, or breast tenderness. It is important that a woman realize that once she has been injected with DMPA, any side effects she may experience cannot be neutralized or eliminated. She has to tolerate these side effects until the medication wears off, typically three months later.
DMPA has also been shown to have a negative effect on bone mineral density, especially with longer-term use; however, studies have shown that her previous bone density is usually restored when the drug is discontinued.
Women may be able to use DMPA when avoidance of estrogen is prudent for medical reasons (see oral contraceptives). A qualified health-care provider should be able to help make the proper distinction. DMPA should not be used by women who have a history of breast cancer, blood clots, liver disease, unexplained vaginal bleeding, or stroke. A woman on DMPA should contact her health-care professional if she experiences a heavy menstrual flow, severe abdominal pain, headaches, or depression.
DMPA injections are over 99% effective if the injections are received according to the correct schedule. A woman using injection contraceptives has the advantage of being capable of becoming pregnant at a later time, if desired, simply by discontinuing use. DMPA does not increase a woman's risk of cancer, including breast cancer, and greatly reduces her risk of developing uterine cancer.
Injectable hormonal contraceptives do not protect against sexually transmitted infections.
Contraceptive patch: Ortho-Evra
An adhesive patch has been developed that provides hormonal contraception through the skin, which is known as a transdermal (through the skin) delivery system. The patch is about the size of a half-dollar and can be worn on the arm, abdomen, or buttocks. A woman wears the patch for a week and then replaces it with a new patch.
These patches are called Ortho-Evra (ethinyl estradiol/norelgestromin patch-topical), and are similar to the pill in that they contain both estrogen and progesterone. Ortho-Evra should be just as effective in preventing pregnancy as the pill. Ortho-Evra is similar to the pill in that it suppresses ovulation and has the advantage of improved compliance and convenience due to weekly administration. A woman only needs to remember to replace the patch once a week instead of being required to remember taking a pill every day. However, some studies have shown that the contraceptive patch may be associated with a greater risk of negative side effects, such as blood-clotting problems, than oral contraceptive pills.
Women who have medical reasons why oral contraceptives are not recommended (such as already having an underlying tendency toward blood clotting) may find that their prescribing physician also recommends against Ortho-Evra because of the similarity in the hormone ingredients of both types of contraceptives.
It is important to ensure that the patch makes good contact with the skin. The patch could be a problem for those women who perspire heavily, swim, and/or take frequent showers because moisture can interfere with the patch's contact with the skin. Some women may also experience skin irritation at the site of the patch. Furthermore, contraceptive failure may be a risk in heavier women (those who weigh over 198 pounds, or 90 kilograms).
As with all other hormonal methods of birth control, the patch will not protect a woman against sexually transmitted infections.
A contraceptive implant known as Implanon is available in the U.S. Implanon provides contraception by the slow release of the progestin etonogestrel over a period of three years. Implanon is a thin rod that is inserted in the upper arm under local anesthesia. Protection from pregnancy occurs within 24 hours of insertion of the rod, and the failure rate is comparable with surgical sterilization (tubal ligations). One advantage of the Implanon rod is that fertility rapidly returns after removal of the rod.
A two-rod implant containing the progestin levonorgestrel (Jadelle) was approved by the FDA for 5 years of use, although it has not been marketed in the United States. Similarly, the Sino-Implant II contraceptive implant is similar to Jadelle, but is designed to remain in place for 4 years.
Preliminary studies of the product showed that it was generally well tolerated and effective in preventing pregnancy. However, these studies showed that irregular bleeding is a possible side effect of the product.
As with all other hormonal methods of birth control, Implanon will not protect a woman against sexually transmitted infections.
Vaginal ring: NuvaRing
A ring-shaped device that contains the hormones estradiol and etonogestrel (a progestin) can be placed in the vagina. It remains in place for three weeks continuously, then it is removed for one week to allow for a menstrual period. It continuously releases low levels of the hormone into the bloodstream for the entire three weeks.
There is currently one brand available in the U.S., NuvaRing (etonogestrel/ethinyl estradiol-vaginal ring). It is about 99% effective in preventing pregnancy, having the same high effectiveness as the other hormonal methods of contraception. The incidence of hormone-related side effects is similar to those seen with other hormonal contraceptive methods such as the pill and the patch. Vaginal discharge can sometimes occur as a side effect of the ring preparation.
NuvaRing does not protect against sexually transmitted infections.
How effective are hormonal birth control methods?
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Medically reviewed by Wayne S. Blocker, MD; Board Certified Obstetrics and Gynecology
Kost K, Singh S, Vaughan B, Trussell J, Bankole A. Estimates of contraceptive failure from the 2002 National Survey of Family Growth. Contraception. 2008;77(1):10-21.