Emergency contraception, commonly known as Plan B, serves as a backup method to prevent pregnancy after unprotected sexual intercourse or contraceptive failure. This medication is available over-the-counter and contains a high dose of levonorgestrel, a synthetic hormone. It can temporarily alter one’s menstrual cycle, a normal response to the hormonal changes it induces.
How Emergency Contraception Works
Plan B primarily works by preventing or delaying ovulation, the release of an egg from the ovary. The high dose of levonorgestrel blocks the surge of luteinizing hormone (LH) that typically precedes ovulation, impeding the egg’s release.
Levonorgestrel can also affect the consistency of cervical mucus, making it thicker. This thickened mucus acts as a barrier, interfering with sperm movement and making it more difficult for them to reach any potential egg. Plan B does not terminate an existing pregnancy; it works before a fertilized egg can implant in the uterus.
Typical Cycle Changes After Taking Emergency Contraception
After taking Plan B, individuals often experience temporary alterations to their menstrual cycle. The timing of the next period can be unpredictable; it may arrive earlier, later, or even at the expected time. Most women will experience their next period within two days to one week of its anticipated date.
Changes in menstrual flow are also common, with some experiencing heavier or lighter bleeding than usual. Spotting or unexpected bleeding between taking the pill and the next period can occur. This breakthrough bleeding can start as early as eight hours after taking Plan B and typically lasts a few days.
Other temporary symptoms may arise due to the hormonal shift. These can include nausea, lower abdominal pain, fatigue, headaches, dizziness, and breast tenderness. These side effects are generally mild and tend to subside within 24 to 48 hours.
Duration of Cycle Alterations
For most individuals, menstrual cycle changes after taking Plan B are confined to the very next cycle. The high dose of levonorgestrel is processed and eliminated from the body within approximately one week.
Subsequent cycles typically return to their regular pattern. Most women observe a return to their normal cycle length within one to two months following emergency contraception use.
These effects are not indicative of long-term disruptions to reproductive health. Persistent or prolonged changes beyond this timeframe are less common and may warrant further attention.
When to Seek Medical Guidance
While temporary cycle changes are expected after taking Plan B, certain situations warrant consulting a healthcare professional. If your next period is delayed by more than a week beyond its expected start date, take a pregnancy test to rule out pregnancy. Plan B is not 100% effective.
Immediate medical attention is necessary if you experience severe lower abdominal pain, especially three to five weeks after taking Plan B, as this could be a sign of an ectopic pregnancy. Unusually heavy or prolonged vaginal bleeding, or if you develop other symptoms typically associated with pregnancy, should also prompt a visit to your doctor.
If side effects such as nausea or headaches persist for more than 48 hours or become severe, seeking medical advice is recommended. Plan B does not protect against sexually transmitted infections (STIs), so if you have concerns about potential exposure, it is important to get tested.