Dear Alice,

On the Planned Parenthood website, it indicates that the copper IUD can be used as emergency contraception if inserted within 5 days of unprotected sex, and that it is 99.9 percent effective as emergency contraception. I had never heard this before. The website also says that the IUD works by affecting the way that sperm move, and that there is no evidence that it works by preventing an embryo from implanting in the uterus. What if the egg meets the sperm in those five days?

Another IUD question. I understand that IUDs are associated with a small increase in risk of pelvic inflammatory disease (PID), which can lead to infertility. I've heard you can have PID which goes symptom-free and undetected. What can a woman do to make sure she doesn't have PID after getting an IUD?


Dear Reader,

Contraceptive technology can certainly be complicated. This may be especially true if sex occurs when a contraceptive method fails or is not used. The copper IUD can, in fact, prevent pregnancy in "emergency" situations. The exact mechanisms aren't fully understood, but the IUD may work by stopping sperm from reaching the egg or by changing the lining of the uterus to prevent a fertilized egg from attaching to the uterus wall.

To understand how a copper IUD can prevent a pregnancy within five days of unprotected sex, a little background info is needed. A common misperception is that conception happens right after sex. However, sperm can actually live inside the uterus for several days. They only cause pregnancy if an egg is available during that window of time, which is why preventing pregnancy is still possible following sex. After fertilization of an egg, it takes another day or so for the egg to implant in the uterus. A pregnancy is not established until a fertilized egg is implanted in the lining of the uterus. All in all, the process of becoming pregnant doesn't happen overnight, which allows some wiggle room for preventing pregnancy through emergency contraception.

On to the IUD: The device is a T-shaped piece of plastic that has copper piping along the "T." It's inserted through the cervix and sits in the uterus to prevent pregnancy. A small amount of copper is released into the uterus immediately after insertion. Copper IUDs trigger anatomical and biochemical changes in the uterus, producing a toxic environment for incoming sperm. The copper IUD doesn't affect ovulation or the menstrual cycle; it immobilizes sperm travelling to the fallopian tubes, thereby preventing fertilization of an egg. When inserted as emergency contraception after unprotected sex, copper IUDs may prevent pregnancy by changing the chemistry in the lining of the uterus so that it's not receptive to a fertilized egg.

Health care providers once believed that IUDs were linked to higher rates of pelvic inflammatory disease (PID), however this association has been refuted. If a person has an infectionand has an IUD inserted, such as chlamydia or gonorrhea, the risk for PID is increased. However, for those without any infections, the risk of PID is not related to IUD use. A health care provider will test for sexually transmitted infections (STIs) before inserting an IUD to avoid any chance of a PID infection.

Using an IUD as emergency contraception involves a visit to your health care provider, which may be difficult to schedule in a time-sensitive situation. It's also a method that can be used as a long-term birth control method (can be used for up to 10 to 12 years) — but if that's not what you're looking for, it's wise to consider other options. The good news is that there are other methods of emergency contraception (EC) are in the form of a safe and effective hormonal pill. Most one-pill formulations of EC, including Plan B One-Step and its generic versions, are available for sale on the retail shelves at many pharmacies and drugstores. For these formulations, no prescriptions are needed and proof-of-age is not required to purchase. They're most effective if taken within 72 hours after sex. However, another type of EC that comes in a pill form, called Ella, is effective up to 120 hours after sex — but it requires a prescription. Interested in learning more about these methods? Take a look at the Q&As about emergency contraception in Go Ask Alice! Sexual and Reproductive Health archives.

Whichever route you choose, know that all forms of emergency contraception are more effective the sooner they are used.

Take care,


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