Plan B, or levonorgestrel emergency contraception, is a high-dose oral contraceptive pill that women can take up to five days after having unprotected sex as a way of preventing pregnancy. Although Plan B, commonly known as the "morning after pill," is available over the counter and has been deemed safe for use by all women, research shows that there are often changes in a woman's monthly menstrual cycle after she takes this medication. However, these changes are generally mild and temporary.
Cycle Changes
You should have a normal period within the next month after taking emergency contraceptive pills. However, you might get your next period as much as a week earlier or later than usual. If you take Plan B before you ovulate, you might get your period earlier than usual. If you take the pill after ovulation, you might start your period later than usual. If your next period is more than one week late, it's a good idea to get a pregnancy test.
Longer Periods
After taking Plan B, you might have a period that lasts longer than usual, particularly if you take the pills in the fourth week of your cycle. And although you might not see any change in the period you have right after you take emergency contraception, the next time you have your period, it could be longer. Women who take Plan B after they ovulate are more likely to have a longer period.
Unexpected bleeding
According to the evidence, most women don't have any bleeding between periods after using Plan B. That said, you do have a higher chance of having irregular bleeding if you've used Plan B than if you haven't. One study found that about 15 percent of women experienced bleeding between periods in the month that they took emergency contraceptive pills. But even if you experience unexpected bleeding, this is not a serious side effect and doesn't indicate that you are having health problems.
Irregular Periods with Repeated Use
If you take Plan B regularly, you might start to experience irregular periods. It's important to know that emergency contraception is not intended to be used as a form of regular birth control because there are many ways to prevent pregnancy that are safer and more effective—for instance, oral contraception and condoms.
