Birth Control Harvard Commentary: The Morning After: How To Avoid Pregnancy With Emergency Contraception October 19, 2000 By Serena Koenig, M.D. Harvard Medical School The ancient Egyptians were one of the first cultures to develop contraception. Obviously, we have come a long way, but the rules remain the same: contraception is effective only when it is used. When used properly, modern methods are extremely effective, but accidents still happen. Keep in mind if you have intercourse without adequate contraception, your odds are up to 1-in-4 that you"ll get pregnant -- depending on the day of your menstrual cycle. The risk, however, drops significantly if you take emergency contraception. If you want to free yourself from worries about accidental pregnancy, talk to your health care provider at your next routine visit. As Jane Sillman, M.D., women"s health expert at Harvard Medical School, suggests, "Be sure to talk to your doctor about emergency contraception and get prescript★ions to keep on hand to use when necessary." There are two main forms of emergency contraception: the morning-after pill, also known as emergency contraceptive pills, and the intrauterine device (IUD). The Morning-After Pill The morning-after pill is not one magic pill, but a routine involving extra birth control pills taken within a particular time frame. The first dose is taken within three days of intercourse, and the second dose is taken 12 hours later. Although we are not exactly sure how the pill works, we believe that it stops or delays ovulation (the release of the egg by the ovary), therefore preventing pregnancy. It is not an abortion pill, which is needed only after pregnancy has definitely occurred. In fact, if more women used emergency contraception, fewer abortions would be necessary. The success rates are slightly different for each type of pill, but the sooner you take the morning-after pill, the more effective it is. For example, the morning-after pill called Plan B (levonorgestrel) is 95 percent effective in preventing pregnancy if taken within 24 hours of intercourse, 85 percent if taken within 24 of 48 hours, and 58 percent if taken within 49 to 72 hours. Anyone can take the morning-after pill, even people who are not already taking birth control pills. Those of you already taking birth control pills can take extra doses of them, or you can purchase emergency contraception kits -- birth control pills packaged specifically for this use. Discuss this with your doctor to find the best plan for you. If you plan to use your own birth control pills, ask your doctor how many pills you should take with each dose. The number will vary depending on the type of pill you take, as different pills contain varying amounts of hormones. If you use the morning-after pill, you should be prepared for some minor side effects. You have about a 50 percent chance of becoming nauseous and a 25 percent chance of vomiting. You can avoid nausea and vomiting in two ways. First, you can take Plan B, because it is the least likely pill to cause nausea. Second, you can ask your doctor for a prescript★ion for an antinausea medicine such as Compazine (prochlorperazine). You should take it one hour before your first dose of the pills. Note: If you vomit within one hour of taking the morning-after pill, you should take it again to ensure maximal effectiveness. The Intrauterine Device An IUD is a small wire implanted into the uterus by a physician in a simple office procedure. If placed within five days of intercourse, it will prevent about 92 percent of pregnancies. IUDs work in two ways: either they induce inflammation (irritation) in the uterus, which prevents fertilization (the joining of the egg and sperm), or they inhibit implantation of the fertilized egg in the uterus. Before considering IUD placement, you will need to discuss the pros and cons with your doctor. IUDs are safe and effective, but they are not appropriate for all women. For example, IUDs should not be placed if you are at risk of a sexually transmitted disease. They are also not usually recommended for women who plan to have future pregnancies. Did The Emergency Contraception Work? When you get your period, you will know that your emergency contraception was effective. If you take the morning-after pill, you may get your period up to two days early or late. If your period is delayed more than seven days, you should take a pregnancy test. Emergency contraception is forgiving, allowing you a second chance. However, it is not a replacement for effective contraception. And more importantly, it does not prevent sexually transmitted diseases. Serena Koenig, M.D., is an instructor in medicine at Harvard Medical School, and on the faculty of the Department of General Medicine at Brigham and Women"s Hospital. She is also the director of medical communications in the Program in Infectious Disease and Social Change at Harvard Medical School. This interview is not intended to provide advice on personal medical matters, nor is it intended to be a substitute for consultation with a physician.