Commonly known as “the morning after pill,” Plan B is a type of emergency contraception that may prevent pregnancy after unprotected sex. It is not the same as RU-486, which is an abortion pill. However, it is controversial in its own right because as of 2009, it became available without a prescription to women aged 17 and over. (Women younger than 17 may still obtain Plan B, but are required to have a prescription.)
Plan B works by delivering a 1.5 milligram dose of a synthetic hormone known as levonorgestrel to your body. Depending on where you are in your cycle, this hormone may prevent or delay ovulation, interfere with egg fertilization, or prevent implantation of a fertilized egg in the uterus by altering the lining, making the environment inhospitable. Plan B is 95% effective when taken within 24 hours of unprotected sex, and 89% effective when taken within 72 hours.
Plan B does have side effects. Your body has to work hard to process the high dose of hormones, so you can reasonably expect to experience fatigue, nausea, headaches, abdominal pain, dizziness, breast tenderness, vomiting, and diarrhea. Additionally, the hormones cause your reproductive system to go through incredibly fast changes in order to prevent pregnancy. Therefore, you can expect an impact on your menstrual cycle as a result. You are likely to experience some spotting up until your next period, and you can expect your next period to be earlier or later than what is normal for you, as well as heavier or lighter than usual. Due to the rapid changes your body must go through to process the hormones in Plan B, you should not rely on Plan B as a primary form of contraception. It is meant to be used only as its name implies- as a backup form of contraception when you are concerned your primary form has failed.