Identification
Plan B is the brand name for a form of emergency contraception. This means that it is designed for use for women who have either had unprotected sex, or have had their usual method of contraception fail (broken condom, for example). Although high doses of certain birth control pills can also function as emergency contraception, Plan B is designed for maximal effectiveness and ease of use. Plan B is a pill that is made up of progestin, which is a hormone that interacts with the female reproductive system. Plan B is available via prescription at most pharmacies, at many student health care centers, and at Planned Parenthood, among other places.
Effectiveness
According to the official Plan B website, Plan B is able to prevent seven out of eight women from becoming pregnant (who otherwise would have become pregnant) after unprotected sex if taken within 72 hours; the medication is even more effective when taken within 24 hours. According to emergencybirthcontrol.org, Plan B, when taken within 24 hours, is 95 percent effective. There are no studies or information available in regards to if the effectiveness is increased by taking the medication within twelve hours, although the general recommendation is to take it "as soon as possible."
Mechanism
The Plan B medication works similarly to other forms of hormonal birth control, although it does provide these hormones at higher levels than other birth control forms. Its primary function is to stop the ovaries from releasing an egg. Because ovulation (egg release) is essential for pregnancy, Plan B is able to prevent pregnancies in this way. In addition, the hormones in the Plan B pill thicken the cervical mucus. The cervical mucus provides an obstacle to sperm trying to reach the egg; thickened mucus can prevent egg fertilization and pregnancy.
