After taking Plan B, three things may happen in a woman's body to prevent pregnancy. WebMD explains that Plan B One-Step may prevent or delay ovulation, interfere with fertilization of an egg or prevent implantation of a fertilized egg by changing the uterine lining. Plan B does not cause miscarriage or abortion, and it does not stop fetal development once a fertilized egg implants in the uterus.
According to WebMD, Plan B is a type of over-the-counter emergency contraception. Its dose is a single pill that contains 1.5 milligrams of levonorgestrel. The risk of pregnancy is reduced by up to 89 percent when Plan B is taken within 72 hours of unprotected sex. When taken within 24 hours, Plan B is about 95 percent effective.
Plan B is not as effective as regular contraception, and it should not be used as a woman's main form of birth control. A woman should not take Plan B if she knows or suspects she is pregnant, has a history of allergy to any ingredients in Plan B or has a history of abnormal vaginal bleeding that has not been evaluated by a doctor. Side effects that may occur after taking Plan B include nausea, abdominal pain, fatigue, headache, dizziness, vomiting and breast tenderness. The medication may also cause unexpected bleeding and menstrual changes, notes WebMD.Learn More
According to WebMD, the effectiveness of Plan B One-Step depends on when it is taken. If taken within 24 hours after unprotected sex, it reduces the risk of pregnancy by up to 95 percent. If taken within 72 hours after unprotected sex, its effectiveness drops to about 89 percent.Full Answer >
According to WebMD, a woman can experience menstrual changes after taking Plan B. Most commonly, a Plan B user experiences lighter periods, heavier periods or irregular spotting for a few weeks after taking the drug.Full Answer >
Taking birth control for less than a week has little effect on the body and menstrual cycle. According to Military Obstetrics & Gynecology, birth control pills do not achieve their full effectiveness until after the first month of use. Many physicians and pill manufacturers suggest that birth control pills become effective after seven days of continuous use.Full Answer >
According to Princeton University, Plan B only protects against pregnancy for 72 hours before and a few hours after taking it. However, the university does say that no one has studied how many hours of protection it provides after taking it.Full Answer >