The birth control patch is a thin, beige plastic square about two inches across that looks like a Band-Aid. It contains progestin and estrogen - hormones found in most birth control pills. Hormones are chemicals that control how different parts of your body work. The patch has a sticky side that can be attached to the skin of the stomach, buttocks, back or upper outer arm.

The hormones in the patch are absorbed into the bloodstream through the skin and prevent pregnancy by keeping the ovaries from releasing eggs. The patch also causes cervical mucus to thicken and the lining of the uterus to thin. This keeps sperm from meeting and fertilizing the egg.

You put a new patch on each week for three weeks (take off the old patch and throw it away). During the fourth week, you do not wear a patch and your period will probably start. After the fourth week, start over again and put on a new patch (even if there is still some bleeding from your period).

• To help you remember, try to put a new patch on the same day each week.

• Put the patch on clean, dry skin and press to make sure it will stay on. Be careful not to touch the sticky side while putting it on your skin.

• Look each day to make sure the patch is still in place.

• It is okay to bathe and swim while wearing a patch.

• It is better not to place the patch on a breast.

If the patch comes loose or falls off, you may need to use another method of birth control, like a condom.

Discuss your medical history with your health care provider before using the patch and let him/her know if you develop any side effects.

Of 100 women who use this method each year, about nine may get pregnant.

The risk of pregnancy is much less for women who use the patch correctly (putting it on the skin the same time each week). The patch may be less effective in women who weigh more than 198 pounds. Certain medications such as Rifampin (taken to treat tuberculosis) and supplements (such as St. John’s Wort) may make the patch less effective.

• Easy to use and does not require the consent of a partner.

• Safe and works well to prevent pregnancy. Using the patch means you do not have to think about birth control when you want to have sex.

• You can see the patch and be reassured it’s still there.

• May make your periods lighter and more regular.

• May reduce menstrual cramps and acne, and strengthen bones.

• Reduces the risk of developing non-cancerous breast tumors and some cancers that affect reproductive organs.

• Does not protect against sexually transmitted infections (STIs), including HIV

• Requires a visit to a health care provider and a prescription

• Certain medications such as Rifampin (taken to treat tuberculosis) and supplements (such as St. John’s Wort) may make the patch less effective.

• It may take a month or two after stopping the patch before normal periods return.

• Some women experience skin irritation where the patch is worn. Others may have breast tenderness.

• It exposes users to higher levels of estrogen compared to most combined oral contraceptives (birth control pills).

• It is not known if serious risks, such as blood clots and strokes, are greater with the patch than with birth control pills and the vaginal ring due to the greater exposure to estrogen.