Progesterone-only birth control methods, which can be pills, injections or intrauterine devices, use only one hormone to prevent pregnancy. This type of birth control is used for women who have trouble tolerating the higher hormone levels in products that contain only estrogen or products that use an estrogen-progesterone combination.
Progesterone-only birth control pills sometimes are referred to as mini-pills. Brands include Nora-BE and Micronor. When you use the mini-pill, you take 28 pills per menstrual cycle, just like with regular birth control pills, except that all of the mini-pills contain progesterone. None have inactive ingredients; therefore, you take them continuously. As soon as you finish one pack, you start the next one. Chances of pregnancy occurring within the first year with the mini pill are about one in 200.
Intrauterine devices (IUDs) are inserted into the uterus to prevent pregnancy. Some are made of a material, such as copper, that acts as a contraceptive, while others are coated with progesterone hormone but contain no other hormones. One such brand of progesterone-coated IUD is Mirena. IUDs are about 99 percent effective in preventing pregnancy. In addition, some IUDs can stay in place for as long as five years, in contrast with others that must be removed and replaced every year.
Another type of progesterone-only birth control is administered by injection, either once a month or once every three months. Depo-Provera is one such product and is delivered every three months. Injectable birth control also has an effectiveness rate of 99 percent. In addition, it may help protect against uterine cancer and is safe to use as soon as six weeks after childbirth or whenever your doctor says it is safe to resume sexual relations. Nursing mothers also can safely use injectable birth control.
Progesterone-only pills may not be as effective as combination pills in preventing pregnancy, and you may have more problems with breakthrough bleeding, or bleeding at any time of the month other than during your normal period.
IUDs can come out of the uterus on their own. For this reason, you must check once a month, usually right after your period, to ensure that you can still feel the strings that are hanging down into your cervix. If you can’t, there is a good chance that the IUD has moved or come out. If this occurs, you may become pregnant.
Injectable birth control is given through a hypodermic needle. If you don’t like needles, you may want to consider another form of progesterone-only birth control.
Side effects of the mini pill include increased risk of a stroke or blood clot, especially if you are a smoker over 35. In addition, the mini pill slightly increases the chances of an ectopic pregnancy, which is a pregnancy that occurs in a fallopian tube rather than the uterus.
If you are using an IUD and become pregnant, it can cause problems with the developing baby. If you cannot feel the IUD and suspect you are pregnant, see your doctor right away.
None of these birth-control methods protect against HIV or sexually transmitted diseases.
Women who have problems with irregular or light periods, high blood pressure, migraine headaches or have breast cancer or a family history of breast cancer are not good candidates for injectable birth control. These are only a few of the contraindications listed by the manufacturers.