How the Morning After Pill Works

History and Facts

The morning after pill, also known as emergency birth control and emergency contraception, has been in use for longer than 30 years, according to the International Consortium for Emergency Contraception. The morning after pill is used to prevent pregnancy after sexual intercourse when sex is forced, contraception fails (such as when a condom breaks) or no birth control method is used. Currently, emergency contraception is registered in 117 countries. Women in 44 countries can obtain the morning after pill directly from a pharmacy or drugstore. In the United States, the morning after pill (Plan B and Plan B One Step) is available without prescription to women 17 years and older, according to experts at the Mayo Clinic. Those 16-years-old or younger must have a prescription from their doctor.

Types

Experts at the Mayo Clinic note that the active ingredients in the morning after pill are a lot like those used in birth control pills, but in much higher dosages. Some brands of emergency contraception contain only the hormone levonorgestrel, such as Plan B and Plan B One Step. Others may contain both progestin, which stops sperm from reaching the ovum and stops a fertilized egg from attaching to the uterine wall; and estrogen, which prevents ovulation.

The morning after pill does not have the same properties as mifepristone, the "abortion pill," states the ICEC. Mifepristone causes a fertilized egg attached to the uterine wall to release, thus terminating a pregnancy. The morning after pill prevents pregnancy from ever occurring. Using EC won't affect an established pregnancy, notes the ICEC.

Use

Planned Parenthood advises taking the morning after pill as soon as possible after unprotected sex. Emergency contraceptionshould ideally be taken within 72 hours after sexual intercourse, with a second dosage taken 12 hours later, notes the Mayo Clinic. Planned Parenthood, on the other hand, states that emergency contraception can be taken 150 hours (five days) after unprotected sex. Some morning after pills, such as Plan B One Step, may be taken in a single dose.

Side Effects

Use of the morning after pill can have side effects, including nausea and vomiting, fatigue, dizziness, headache and abdominal pain. Planned Parenthood indicates that menstruation may occur earlier or later than usual; it may also be heavier or lighter or completely normal. Women who don't get their period three weeks after taking the morning after pill or who experience signs of pregnancy should contact their doctor.

Impact

Planned Parenthood states that use of Plan B reduces the possibility of pregnancy by 89 percent if taken within 72 hours after having unprotected sex. However, the morning after pill's effects are far-reaching: the ICEC estimates that in 2000, women's access to the morning after pill prevented around 51,000 abortions in the United States Between 1994 and 2000, during which there was an 11 percent decrease in abortions in the U.S., 43 percent were due to use of the morning after pill.