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Am Fam Physician. 2003;67(7):1575-1576

What is a progestin-only contraceptive?

A progestin-only contraceptive is one kind of birth control pill. It is often called the “mini-pill.” Regular birth control pills have two female hormones: estrogen and progestin. The mini-pill has only progestin in it. Because this pill does not contain estrogen, it may not have as many side effects.

How does the progestin-only contraceptive work?

This contraceptive does three things. First, like regular birth control pills, the progestin-only pill makes your body “think” that you are pregnant and stops your ovary from releasing an egg. Second, the mini-pill causes changes in your uterus. (The uterus is where a baby grows.) Because of the changes caused by progestin, your uterus is less likely to let a pregnancy get started even if an egg is released.

Third, the progestin-only pill thickens the mucus between your uterus and your vagina. Sperm have a hard time getting through the thick mucus to reach the egg.

Is the progestin-only pill better than regular birth control pills?

The progestin-only pill is better than regular birth control pills if you are breastfeeding because the mini-pill will not change your milk production.

The mini-pill may be safer for some women to use. This pill is safe for women who are older than 35 years. It is also safer for women who smoke, have high blood pressure, are overweight, or have a history of blood clots. Regular birth control pills make some women feel sick to their stomach. The progestin-only pill might not cause this problem.

If I use the progestin-only pill, can I still get pregnant?

No contraceptive method is perfect, even when you use it the right way. Two or three of every 100 women who use the progestin-only pill the right way could still get pregnant. This risk of pregnancy is almost the same as the risk with regular birth control pills. Remember that both kinds of birth control pills are better at preventing pregnancy than condoms.

Does the progestin-only pill have any disadvantages?

You might have a little bleeding between your periods for several months after you start taking the progestin-only pill. This can be inconvenient, but it is not a health risk. The bleeding will probably go away on its own after you use the mini-pill for a few months. If the bleeding seems heavy or if it bothers you, you can talk to your doctor about it.

Common side effects of the mini-pill are weight gain (which usually goes away when you stop taking the pill), tender breasts, and bleeding between your periods.

Like regular birth control pills, the progestin-only pill has to be taken for a whole month before it can start to protect you from pregnancy. So for the first month, you need to use another kind of contraception, such as condoms, along with the mini-pill.

The mini-pill only works if you take it every day at the same time of day. If you are more than three hours late taking the pill, you have to use a second method of contraception (such as condoms or not having any sex at all) until your next period, to prevent a possible pregnancy.

If you forget to take a mini-pill for even one day, you have to use a second method of contraception until your next period. You cannot take two pills the next day to make up for a missed pill, the way you can with regular birth control pills.

Like all birth control pills, the progestin-only pill does not protect you from getting a sexually transmitted disease.

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