Plan B is an emergency contraceptive designed to prevent pregnancy after unprotected sexual intercourse or contraceptive failure. This medication serves as a backup method, offering a crucial option when regular birth control methods are not used or do not work as intended.
What is Plan B?
Plan B is an over-the-counter emergency contraceptive pill. It contains a synthetic hormone called levonorgestrel, which is a progestin. This medication is not intended for routine use as a primary form of birth control, but rather for emergency situations. Plan B is widely accessible without a prescription, making it readily available for those who need it quickly.
The Science of Ovulation Delay
Ovulation is the process where a mature egg is released from an ovary, making it available for fertilization by sperm. The levonorgestrel in Plan B acts by preventing or delaying the luteinizing hormone (LH) surge. The LH surge is a rapid increase in LH levels that signals the ovary to release an egg.
By disrupting this hormonal signal, Plan B prevents the egg from being released from the follicle. If ovulation does not occur, there is no egg available to be fertilized by sperm, thereby preventing pregnancy. Levonorgestrel specifically targets this pre-ovulatory phase, making it ineffective if ovulation has already happened.
Timing and Effectiveness
The effectiveness of Plan B is highly dependent on when it is taken relative to unprotected sex and the menstrual cycle. It works best when taken as soon as possible, ideally within 72 hours (three days) after unprotected sex. Some studies suggest it can have some effectiveness up to 120 hours (five days), but its efficacy decreases significantly with time. The earlier the pill is administered, the more likely it is to successfully delay ovulation. Plan B cannot prevent pregnancy if ovulation has already occurred. Its mechanism relies on interfering with the process of egg release, not on affecting a fertilized egg or an existing pregnancy. Therefore, if an egg has already been released and fertilized, or if implantation has begun, Plan B will not be effective.
Common Misconceptions and Side Effects
A common misunderstanding is that Plan B is an abortion pill, but this is not accurate. Plan B works by preventing ovulation, meaning it prevents a pregnancy from occurring in the first place; it does not terminate an existing pregnancy. It will not work if a person is already pregnant and does not affect an implanted embryo. Abortion pills, by contrast, work by ending an established pregnancy.
Plan B is generally considered safe, with side effects that are typically mild and temporary. Common side effects can include nausea, abdominal pain, fatigue, headache, dizziness, and breast tenderness. Changes to the menstrual period, such as it being earlier, later, heavier, or lighter, or experiencing spotting, are also frequently reported. These effects usually resolve within a few days.