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Birth Control Pills

Oral Contraceptives


About birth control pills

Birth control pills are the most commonly used form of reversible contraception in the United States. When used correctly and consistently, they are also one of the most effective methods of preventing pregnancy. More than 11 million women in the United States use birth control pills, and they are the most popular form of contraception for women under age 30, according to the Centers for Disease Control and Prevention (CDC). In 2002, oral contraception was the most frequently used method of birth control for women aged 15 to 44 years old.

Also known as “the pill,” birth control pills are made of low doses of synthetic female hormones (usually a combination of estrogen and progestin, synthetic progesterone). First approved by the Food and Drug Administration (FDA) in 1960, birth control pills prevent pregnancy by preventing ovulation (the monthly release of an egg from an ovary). The pills also suppress the hormones that prepare the uterus to receive the fertilized egg and establish pregnancy. In doing so, they actually “fool” the body into thinking that the woman is already pregnant, which creates an environment that makes fertilization difficult.

At the beginning of a woman’s menstrual cycle, levels of estrogen begin building up. This causes the endometrium (the lining of the uterus) to thicken in preparation for a fertilized egg. Approximately 14 days into the cycle, the level of estrogen peaks and an egg is released from one of the ovaries. Following ovulation, the levels of progesterone rise. Lasting for seven days, this rise further prepares the endometrium for conception. If conception does not occur, levels of estrogen and progesterone drop to their lowest point. This drop causes the uterine lining to shed, resulting in menstruation.

When a woman takes birth control pills, however, hormone levels are maintained at set levels. By preventing the level of estrogen from peaking, the pill prevents the body from signaling the ovary to release an egg. Pregnancy is not possible without the release of an egg. Birth control pills also prevent pregnancy by causing the mucus in the cervix to thicken. This makes it difficult for sperm to enter the upper genital tract to fertilize an egg that may have been released. The endometrium also remains thin in women who take the pill, which hinders conception because it prevents the implantation of a fertilized egg.

In order for birth control pills to work effectively, a woman must remember to take the pill every day at the same time of day. When always used correctly, birth control pills have an effectiveness rate of more than 99 percent. Under typical use (less than perfect use), the effectiveness rate drops to 95 percent. This effectiveness may be further reduced by some medications, including certain antibiotics.

A reversible form of contraception, birth control pills usually allow women to conceive within a few months of discontinuing use. For some women, there may be only a two-week delay before they begin to ovulate again. Although it may take longer, most women can become pregnant in about one to three months. This time period, however, can vary greatly among women due to contributing factors, such as age and gynecological health.


Types and differences of birth control pills

Different types of birth control pills contain different hormones. Most prescriptions contain estrogen and progestin (synthetic progesterone), but a few varieties contain only progestin (progestin-only pills [POPs]). Also known as the “mini-pill,” POPs always come in 28-day packs, and all the pills in those packs contain progestin. To prevent pregnancy, the pills must be taken at a certain time every day. If a woman is late taking the medication by only three hours, she will need to use a backup contraceptive for the next two days.

Although POPs are not as effective as pills containing both estrogen and progestin, they are a useful option for many women. Because estrogen reduces milk production, POPs may be recommended for women who are breastfeeding. The pills may also be recommended for women who cannot take estrogen, including women with a history of certain cancers (e.g., breast cancer) or blood clots.

Birth control pills containing estrogen and progestin are known as combined birth control pills. They come in either a 21-day, 28-day or 91-day cycle. A 21-day cycle means that a patient takes one pill each day for 21 days, and then waits seven days (during which she will experience “withdrawal bleeding” and other menstrual-like symptoms due to the drop in hormone levels) before beginning another pack of 21 pills. Although it simulates a woman’s monthly period, this withdrawal bleeding is not like a normal menstrual period.

A 28-day cycle means that the patient takes a pill every day for 28 days and then starts another pack of 28 pills. The last seven pills in a 28-day pack have a placebo effect so that there is also a drop in the levels of hormones and a woman experiences her period-like (withdrawal) bleeding. These seven pills are a different color than the other pills and contain different ingredients, depending on the particular prescription:

  • The last seven pills may be inert (containing no medication). These are also known as “sugar pills.”
  • In other prescriptions, the last seven pills deliver low doses of estrogen on days 22 to 28.
  • Another type of birth control pill contains iron in the seven “inert” pills. Because women are losing menstrual blood during these seven days, the iron pills can help maintain healthy iron levels.

The active pills contain different dosages of hormones, depending on the prescription. The pills may be:

  • Monophasic (one-phase), in which all the “active” pills contain the same dose of hormones.
  • Biphasic (two-phase), in which patients take pills of a certain dose for the first phase of the cycle and then a different dose for the second phase. The color of the pills changes as the dose changes.
  • Triphasic (three-phase), in which doses change three times, with the number of days of each dose ranging between five and 10. The color of the pills changes as the dose changes.

It should be noted that the 21- and 28-cycle birth control pills are designed with either no-pill or placebo-pill periods – during which bleeding occurs – to increase women’s comfort level with taking such medication. Because women are used to having a monthly menstrual period, some women may view it as unsafe or unnatural not to bleed every month, and others may see their periods as confirmation that pregnancy has not occurred. However, withdrawal bleeding is not medically necessary or related in any way to the effectiveness of birth control pills.

In 2003, the Food and Drug Administration (FDA) approved a 91-day cycle of birth control pills. These extended-cycle pills are taken for 12 weeks (84 days), followed by seven placebo pills. A new packet is then started after the 91st tablet. By prolonging the number of active pills, this regimen reduces the number of periods from once a month to about once every three months. Women may experience more unplanned bleeding or spotting than with either 21-day or 28-day pills. Although the continuous pill is generally considered safe, the long-term safety is not yet established.

The FDA also approved another type of extended-cycle birth control pill in May 2006. This pill also reduces the monthly period to only four per year. However, instead of seven placebo pills, women receive a low dose of estrogen during their bleeding episodes. The estrogen may provide a lower risk of breakthrough bleeding and spotting between the bleeding episodes. The pill is now available by prescription.

In addition, the FDA is reviewing another form of oral contraceptives that do not include any placebo pills and should, therefore, theoretically eliminate episodes of withdrawal bleeding altogether. Initial clinical trials have found the new pills to be as effective in preventing pregnancy as other forms of oral contraception as well as helping alleviate symptoms such as dysmenorrhea, menorrhagia and menstrual migraines. The new extended birth control pills may be available by prescription soon. Women interested in the new pill should consult with their ObGyn.

In the United States alone, there are more than 40 brands of birth control pills available. These include:

Progestin-only pills:

Generic NameBrand Name


Micronor, Nor-QD



Combined birth control pills:

Generic NameBrand Name

desogestrel and ethinyl estradiol

Apri, Cyclessa, Desogen, Mircette, Ortho-Cept

drospirenone and ethinyl estradiol


levonorgestrel and ethinyl estradiol

Alesse, Aviane, Levlen, Levlite, Levora, Nordette, Tri-Levlen, Seasonale, Seasonique, Triphasil, Triphasil, Trivora

ethynodiol diacetate and ethinyl estradiol

Demulen, Zovia

norethindrone and ethinyl estradiol

Brevicon, Genora 0.5/35, Genora 1/35, Intercon 0.5/35, Intercon 1/35, Jenest, Modicon, Necon (0.5/35, 1/35 or 10/11), Nelova (0.5/35E, 1/35E or 10/11), Norethin 1/35E, Norinyl (1+35 or 1+50), N.E.E., Ortho-Novum, Ortho–Novum 1/35, Ortho Novum (7/7/7 or 10/11), Ovcon, Tri-Norinyl

norethindrone acetate and ethinyl estradiol

Estrostep, Loestrin

norethindrone and mestranol

Genora 1/50, Nelova 1/50M, Intercon 1/50, Necon 1/50, Norethin 1/50 M, Norinyl 1/50, Ortho–Novum 1/50

norgestimate and ethinyl estradiol

Ortho-Cyclen, Ortho Tri-Cyclen

norgestrel and ethinyl estradiol

Low-Ogestrel, Ogestrel, Ovral, Lo/Ovral

Brands of birth control pills contain slightly different medications or doses, may be taken differently and have varied risks and benefits. Women should know the exact brand of pills they are using and carefully follow usage instructions.


Conditions treated with birth control pills

The most common reason for prescribing birth control pills is to prevent pregnancy. However, there are some conditions that are treated with oral contraceptives. These include:

  • Amenorrhea. Absence of menstruation.
  • Dysmenorrhea. Abnormally painful menstruation.
  • Hypermenorrhea. Abnormally heavy menstrual bleeding.
  • Hyperandrogenism. An overproduction of male hormones, usually by the ovaries.
  • Hirsutism. Abnormal hair growth in females, usually on the neck or face. The pill cannot reduce or eliminate any existing hair growth, but should prevent or reduce additional hair growth. Patients taking birth control pills to control this condition will usually need to wait six to 12 months to see any reduction in hair growth.
  • Polycystic ovarian syndrome. A grouping of symptoms, including many of the above (amenorrhea, hirsutism and hyperandrogenism) as well as infertility and the formation of many tiny ovarian cysts.
  • Endometriosis. A painful condition in which the lining of the uterus grows outside the uterus, frequently in other reproductive organs. Patients taking birth control pills for endometriosis may need to follow different directions than on the package. Instead of taking the pills for 21 days and then taking a break for seven, patients may be instructed to take another cycle of 21 pills immediately. Doing this continuously will prevent the patient from menstruating at all. Menstruation for women with endometriosis can be extremely painful, and in some cases, reducing the number of menstrual cycles per year is necessary.
  • Irregular periods.
  • Dysfunctional uterine bleeding (DUB). Abnormal vaginal bleeding that occurs during a menstrual cycle in which ovulation does not take place.
  • Acne.

Women who do not regularly take birth control pills can use a higher dose form in a one-time emergency if they had unprotected sex but do not want to become pregnant (emergency contraception). The Food and Drug Administration approved the sale of levonorgestrel (Plan B) without prescription for women aged 18 and older in August 2006. Levonorgestrel, commonly referred as the morning-after pill, contains a high dose of the most common ingredients in regular birth control pills. Taken within 72 hours of unprotected sex, the two-pill series can significantly reduce the chance of pregnancy. Women are encouraged to take the pills with food to reduce the risk of nausea and/or vomiting. However, this method will not work if taken more than one time during a one-month period, or if a patient is already pregnant.

Conditions of concern

Though today’s low-dose birth control pills are safe and effective for the majority of women who take them, some conditions present potential risks. Women need to discuss the use of the pill with their physician to determine if it is a safe form of birth control. Conditions that may prevent a woman from using birth control pills include:

  • Thyroid disease
  • Breast, cervical, uterine or liver cancer in her personal or family medical history
  • Deep vein thrombosis or any other blood clot disorders
  • History of stroke
  • Depression
  • Migraine headaches
  • Certain heart conditions (e.g., coronary heart disease, heart failure)
  • Kidney failure
  • Hepatitis
  • Abnormal changes in menstrual or uterine bleeding
  • Endometriosis
  • Uterine fibroids

The use of birth control pills is also a concern in women with other conditions, including:

  • Family history of heart disease
  • High blood pressure
  • High blood cholesterol
  • Diabetes
  • Non-cancerous breast disease (fibrocystic breasts)
  • Gallbladder disease or gallstones
  • Liver disease
  • Epilepsy
  • Lupus
  • Sickle cell anemia
  • Chorea gravidarum (chorea [a condition causing jerky body movements] occurring during pregnancy)

Women are also encouraged to speak with their physician before taking birth control pills if they are breastfeeding, or if they smoke.


Potential benefits of birth control pills

Birth control pills offer women numerous benefits over other forms of contraception. These include:

  • Making periods more regular, lighter or less frequent (extended-cycle pill).
  • Reducing cramps.
  • Not interfering with intercourse. No preparation is necessary before, during or after sexual intercourse.
  • Lessens the symptoms of premenstrual syndrome.
  • The long-term safety is well established. The pill has been studied for more than 40 years.
  • Reversible form of contraception, offering a relatively quick return to fertility.
  • Highly effective when used consistently and correctly.

In addition to preventing pregnancy and making a woman’s menstrual cycle more regular, birth control pills offer women a number of significant health benefits. As documented in the package insert of every pack of pills, taking birth control pills reduces a woman’s risk of the following conditions:

  • Colorectal cancer
  • Ovarian cancer
  • Ovarian cysts (low- dose pills may not provide the same benefit)
  • Pelvic inflammatory disease
  • Endometrial cancer
  • Iron-deficiency anemia

Other potential benefits include:

  • Prevention of ectopic pregnancy
  • Decreased acne
  • Prevention of bone density loss for women who have attained their peak bone mass (generally those over 30)
  • Improvements in hirsutism (excessive hair)
  • Improvements in endometriosis
  • Improvements in rheumatoid arthritis
  • Desirable effects on cholesterol levels (HDL and LDL)
  • Decrease in non-cancerous breast disease and breast cysts (fibrocystic breasts)
Side effects

Potential side effects of birth control pills

Although today’s birth control pills use much lower hormone levels than in the past, they still may cause a variety of side effects. Common side effects of birth control pills include:

  • Irregular bleeding (e.g., spotting or breakthrough bleeding)
  • Amenorrhea (a condition in which women no longer get their period)
  • Abdominal cramping
  • Bloating
  • Mood swings
  • Acne
  • Breast pain, tenderness or swelling
  • Dizziness
  • Nausea or vomiting
  • Unusual tiredness or weakness
  • Headaches or migraines
  • Depression

Less common side effects include:

  • Vaginal infection with swelling, redness, burning or itching of the vagina or white discharge
  • Painful or missed periods
  • Brown, blotchy spots on exposed skin
  • Gain or loss of body or facial hair
  • Increased or decreased interest in sexual intercourse
  • Increased sensitivity of skin to sunlight
  • Weight gain or loss
  • Change in appetite
  • Difficulty wearing contact lenses
  • Rash

Other possible side effects include:

  • Lumps in breast (in women with a history of fibrocystic breasts)
  • Pains in stomach, side or abdomen
  • Yellowing of the eyes or skin (jaundice) in women who smoke
  • Swelling of the ankles or feet
  • Diarrhea or constipation
  • Gingivitis
  • Bulging eyes
  • Fever
  • Change in color of urine or stool

One of the most common side effects of birth control pills is bleeding during the first three months (metrorrhagia). This is called spotting when slight or breakthrough when heavy. Women are generally advised to continue taking the pill as prescribed and wait one week before contacting their physician. After three months, women should report any missed or irregular menstrual periods and any irregular vaginal bleeding that they may experience.

The most common side effects associated with birth control pills do not require medical attention. However, symptoms that are bothersome should be reported to a physician, and patients should seek immediate emergency medical assistance if they experience any of the following:

  • Leg pain or tenderness (which could be a sign of a blood clot)
  • Any symptoms of a possible stroke, which include confusion, dizziness, nausea and/or vomiting, severe headache or numbness/weakness on one side of the body
  • Chest pain (which could be a sign of a heart attack)

Drug or other interactions

Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. These substances may interfere with the effectiveness of birth control pills, or cause other complications.

Birth control pills can increase the risk of side effects from the following medications:

  • Benzodiazepines. Medications used to relieve anxiety.
  • Corticosteroids. Cortisone-like medications used to treat inflammation, itchiness, swelling and allergic reactions.
  • Immunosuppressants. Medications used to suppress the body’s immune system.
  • Theophylline. Medication used to treat asthma and other lung diseases.

When taken along with birth control pills, other medications can decrease the effectiveness of the pill or increase the risk of liver damage. They include:

  • Antibiotics. Medications used to treat bacterial infections.
  • Hormone replacement therapy or other forms of estrogen.
  • Antiarrhythmics. Medications used to treat arrhythmias (abnormal heart rhythms).
  • Antihypertensives. Medications used to treat high blood pressure (hypertension).
  • Disulfiram. A medication used to help people overcome drinking problems by making the taste of alcoholic beverages unappealing.
  • Narcotic antagonists. Medications that block the effect of narcotic drugs to assist addicts in refraining from drug use. They are also used in the treatment of alcoholism.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs). Medications used to treat inflammation.
  • Anabolic steroids. Medications similar to the male hormone testosterone that are used to rebuild weak body tissue due to a serious injury or illness. They are used in the treatment of certain types of infections, anemia, cancers and edema.
  • Androgens. Male hormones that are used in the treatment of developmental or hormonal conditions in men, endometriosis and some forms of breast cancer in women.
  • Barbiturates. Medications once commonly used in the treatment of anxiety, tension, insomnia, epilepsy and other conditions. Because this medication is easily habit-forming, it has generally been replaced by less addictive medications.
  • Anticonvulsants. Medications used to control or prevent seizures (convulsions).
  • Gold compounds. Medications used in the treatment of rheumatoid arthritis.
  • Antifungals. Medications used to treat fungal infections.
  • Antiprotozoals. Medications used to treat parasitic infections.
  • Phenothiazines. Medications used to treat some mental disorders, including schizophrenia and psychosis.
  • Antibacterials. Medications administered to treat bacterial infections or to prevent infections in high-risk individuals, such as those with HIV/AIDS.
  • Some migraine medications, muscle relaxants and cancer-fighting drugs.

Lifestyle considerations

Birth control pills take time to work. Though the majority of pills are effective in most women after seven days, it is recommended that women continue to use another form of contraception while taking their first full pack of pills. Patients are encouraged to leave the pills in their original container, which helps women keep track of their medication. This is vital because the pills must be taken on time (ideally no more than 24 hours apart) and in proper order to ensure their effectiveness. To prevent lapses in taking the medication, patients are advised to have an extra month’s supply on hand at all times, replacing it each month. They should also have an adequate supply when traveling to areas where the pills may not be available.

Women on birth control pills will need to see their gynecologist once a year. Their checkup should include a blood pressure measurement, breast and pelvic exams as well as a Pap test. Some women may require more frequent follow-up visits depending on their gynecological health.

Women should immediately stop taking birth control pills if they become pregnant, or suspect they might be pregnant, to prevent serious consequences for the unborn child. Women who recently delivered a baby and who are not breastfeeding may resume taking birth control pills two weeks after the birth. However, pills that contain estrogen are not recommended while breastfeeding because they can decrease the amount or quality of breast milk or even pass through the milk into the feeding infant. Some physicians prescribe progestin-only pills for breastfeeding mothers, but recent research has suggested that this practice may increase women’s risk of diabetes if they had gestational diabetes during their pregnancy. More studies are necessary to confirm this link.

Potential risks of birth control pills

Although they are safe for most women, birth control pills do carry some risks. Potential risks include:

  • Increased risk of cervical cancer
  • Elevated blood pressure
  • Formation of blood clots in the deep veins of the body
  • Increased risk of stroke and heart attack
  • Worsening of diabetes
  • Blockage of the arteries
  • Increased risk of gallstones
  • Increased risk of benign (non-cancerous) liver tumors

Women taking birth control pills are urged not to smoke. Cigarette smoking may decrease the effectiveness of the pill and may increase the risk of heart attacks, strokes and blood clots. This risk is higher for women over the age of 35 and women who smoke 15 or more cigarettes a day.

Birth control pills do not offer protection against human immunodeficiency virus (HIV) or other sexually transmitted diseases (STDs). Condoms should be used along with the pill to prevent the transmission of STDs.

It is unclear whether birth control pills increase a woman’s risk of developing breast cancer. Studies have provided mixed results. The link between liver cancer and current forms of birth control pills is also unclear. Women are encouraged to discuss these and all other risks with their physician.

Questions for your doctor on birth control pills

Patients may wish to ask their doctor or healthcare professional the following questions about birth control pills:
  1. Are birth control pills safe for me to take?
  2. What type of pill would be best for me?
  3. What are the risks associated with this pill?
  4. Can I use an extended-cycle birth control pill?
  5. Do I have to take the pills at the exact same time every day?
  6. What should I do if I miss a pill?
  7. Can I take a different dose of pills as a form of emergency contraception?
  8. What are some of the common side effects of birth control pills?
  9. What side effects require medical attention?
  10. What medications lessen the effectiveness of birth control pills?
  11. How long do I have to take birth control pills before they begin to take effect?
  12. How soon can I become pregnant after I stop taking birth control pills?


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