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Reviewed by the Faculty of Harvard Medical School

Frequently Asked Questions: Birth Control

Can you get pregnant from having sex just once?

You have about a one in four chance of becoming pregnant, if you have sex without using birth control during the middle two weeks of your menstrual cycle. It is better to use some method of birth control than to "take a chance" and not use any protection, especially if you have no desire and now is not the time to become pregnant. Also, not using condoms increases the risk of getting infected with a sexually transmitted disease (STD) such as HIV/AIDS. Latex condoms help to prevent the spread of HIV and are a wise choice if you or your partner could potentially be infected with an STD.

Can you tell if someone has a sexually transmitted disease just by looking at him or her?

Some STDs have visible symptoms such as open sores or ulcers in the genital area or an unusually green or yellow discharge. Others can only be identified by blood tests. People with these STDs may not know they are infected because they have not developed symptoms, yet they can still infect you. Take every precaution to protect yourself by using latex condoms.

Is the withdrawal method an effective form of birth control?

The withdrawal method, in which the male withdraws his penis, is not a reliable method of birth control. The ejaculation fluid or semen contains millions of sperm, but small drops often are released from the penis even before ejaculation. These small drops of semen may contain hundreds to thousands of sperm, and are just as likely to cause pregnancy as a complete ejaculation.

Moreover, the withdrawal method is difficult. Men may not withdraw in time and may ejaculate before pulling out. Even if a man withdraws in time, ejaculation fluid may be released, coming into contact with his partner's external genitalia. This is not safe because sperm are highly mobile and may travel into the vagina, where they may encounter an available egg, resulting in an unplanned pregnancy.

What should I do if a condom breaks?

Do not panic. There are several options to help couples deal with this emergency. The emergency toll-free hotlines (800) 230-PLAN (7526) and (888)668-2528 provide information and assistance, particularly for women who need emergency contraception but cannot reach or do not have a health-care provider. Another option is to ask your health-care provider for prepackaged emergency birth control, known as an "emergency contraception kit." This kit of hormones is available by prescription. You can also get a prescription for the morning-after pill (also called emergency birth control) ahead of time. Women should talk with their health-care provider about ways to effectively manage an emergency situation.

What kind of condom can I use if I am allergic to latex?

Condoms made of polyurethane, silicone rubber, or natural skin (lambskin) are available. Most condoms are made of latex and have been proven to protect against HIV, sexually transmitted infections, such as gonorrhea and chlamydia, and probably human papilloma virus, the virus that causes genital warts. Polyurethane condoms have not been proven to protect against HIV and other STDs. Lambskin condoms block sperm and protect against pregnancy, but not infection.

Aren't all birth-control pills basically the same?

Not exactly, although all birth-control pills prevent pregnancy. There are two main forms: the combination pill and the mini-pill. The combination pill contains both estrogen and progesterone hormones, whereas the mini-pill contains only progesterone. Depending on the brand of combination pill, the estrogen and progesterone content may vary in type and amount. If you experience a side effect from one form or brand, speak with your health-care provider to review other options. There may be a more suitable form or brand of birth-control pill for you.

Is it normal to experience breakthrough menstrual bleeding while using birth-control pills?

In general, about 10 percent to 30 percent of women using the birth-control pill experience irregular menstrual bleeding (referred to as "breakthrough bleeding"). This generally happens within the first three months of beginning the pill, and it usually goes away by itself.

Irregular menstrual bleeding that develops or continues after the first three months or after several years of using the pill requires further evaluation. Although women who experience irregular bleeding while taking the pill do not need to stop using this form of birth control, they should speak with their health-care provider Proper evaluation and treatment are important. Irregular menstrual bleeding usually can be treated by switching to a different type of pill.

Do birth-control pills interact with other drugs?

It is almost impossible to list every possible drug interaction that may occur with birth-control pills. For example, women taking antibiotics are often advised to use a back-up method of birth control for at least two weeks. Although there is no hard evidence that most antibiotics decrease the effectiveness of birth-control pills, certain antibiotics may change the intestine's normal bacterial population and interfere with absorption of the birth-control pill, or they may speed up the rate of drug metabolism, making the pill less effective. As a precaution, it is easier to use a backup method of birth control rather than worry about the risk of pregnancy.

Several other medications can interfere with the birth-control pill by interfering with the liver's ability to process and remove hormones from the bloodstream. A back-up method of birth control should be used by anyone who is using any of the following:

  • Anti-seizure medications, such as phenytoin or carbamazepine
  • Sedatives, such as phenobarbital
  • Antifungal medication, such as griseofulvin
  • Anti-tuberculosis medication, such as rifampin
  • Some herbal supplements, such as St. John's wort
Does it matter if I occasionally miss a dose of the birth control pill, injectable birth control or other hormonal methods?

Hormonal contraceptives should be taken as prescribed to provide reliable and consistent protection. When it comes to missing a dose, some hormonal contraceptives are more forgiving than others, but these medications are more effective when they are taken exactly as prescribed.

Combination birth-control pills need to be taken daily. However, it's possible to miss up to two doses and still be protected against pregnancy as long as you immediately take the two pills that you missed. If more than two pills are missed, then it is best to stop taking the pill for that month. Allow menstruation to take place, and start a new pack with your next menstrual cycle. A back-up method, usually condoms or abstinence, should be used during this time to prevent pregnancy. Always call your health-care provider if you miss more than two pills or you are unsure of what to do.

Mini-pills are more sensitive to missed or delayed doses because each dose protects for just 24 hours. A back-up birth control method is necessary for at least two days if you miss a dose (even if it is delayed by only three hours).

Progesterone injections, normally given every 12 weeks, should not be skipped or delayed because ovulation and fertility can quickly begin again, without your knowledge. A missed shot increases the risk of pregnancy unless abstinence or another reliable back-up birth control method is used. If no back-up method is used, pregnancy must be ruled out before you resume the injections.

Estrogen and progesterone injections, normally given monthly, are also sensitive to delayed or missed doses. If no back-up method of birth control is used, pregnancy must be ruled out before the injections are resumed.

Does Depo-Provera cause hair loss?

Some women do experience hair loss, known as alopecia after Depo-Provera injections. Scalp hairs are in a balance between a resting phase and an active growth phase, with most of the hairs in the active growth phase. During the growth phase, new hairs are always growing and replace natural hair loss. During the resting phase, the hairs stop growing and lost hairs are not replaced. The resting phase is more sensitive to hormonal changes and may delay the normal transition time back to the growth phase.

Why some women experience hair loss with Depo-Provera is unclear but it is believed to be the result of a prolonged resting phase. The loss of hair is short-lived, and patterns of hair growth usually return to normal. On rare occasions, Depo-Provera may cause significant hair loss and should be discontinued.

Who are the best candidates for intrauterine devices (IUDs)?

The most important consideration when choosing an IUD is a woman's likelihood of developing a sexually transmitted disease such as gonorrhea or chlamydia. If a woman develops a sexually transmitted disease, and she has an IUD in place, she may have a higher risk that the infection will spread from the cervix to the upper reproductive organs (uterus, fallopian tubes, and ovaries) a condition called pelvic inflammatory disease (PID). PID can lead to infertility and other complications. This means the best candidates for using an IUD are women in steady relationships, whose partners are reliable and monogamous (neither partner having sex with anyone else), as they have a very low rate of developing an STD. Age is also a factor. IUDs are generally not advised for teenagers, as they have a higher rate of STDs, and they are also more likely to report more menstrual pain and bleeding and rejection of the IUD compared to women older than 20.

Can you change your mind after having a tubal ligation or vasectomy?

Tubal ligation (for women) and vasectomy (for men) are two surgeries that prevent pregnancy. Reversing either is possible, but it is difficult, costly and may be unsuccessful.

An infertility surgeon can reverse a tubal ligation. However, this is usually not covered by health insurance. The cost of hospitalization and surgery may be significant. In addition, reversal of tubal ligation is more likely to lead to an ectopic pregnancy or a pregnancy located somewhere other than the uterus.

The chance of getting pregnant after a tubal ligation has been reversed depends on how much healthy tissue remained after the original tubal ligation. If electrocautery (use of heat-generating instruments for cutting and burning) was used for the tubal ligation, then tissue damage may be great so that this type of tubal ligation is difficult to reverse. However, reversal has led to a successful pregnancy in approximately 30 percent to 60 percent of cases.

If clips or Falope Rings were used for the tubal ligation, the tissue damage may be less severe than that associated with electrocautery. Reversal of a vasectomy has led to a successful pregnancy in up to 70 percent of cases.

A vasectomy is easier to reverse than a tubal ligation, but it is a costly and complicated surgery. Reversal of a vasectomy has led to a successful pregnancy in at least 50 percent of cases.

In addition to reversal of the sterilization procedure, couples that change their minds may consider IVF to assist in becoming pregnant. However this procedure is also expensive and may not be successful.

Should I use the same method of birth control for my entire reproductive life?

Each method of birth control has advantages and disadvantages, the importance of which varies with one's age. As you age, your lifestyle changes and so do your priorities and preferences. Barrier methods can be used throughout one's reproductive life, but there are many safe, effective and convenient methods available that you may find more suitable. You should familiarize yourself with all the methods and choose one that best suits your needs.

Last updated September 17, 2010