In addition, it may inhibit implantation by altering the endometrium. Plan B is not effective if a woman is pregnant. Plan B cannot terminate an established pregnancy. Plan B reduces the risk of pregnancy among users from about eight percent to about one percent. In other words, when used correctly, it reduces the risk of pregnancy by 89 percent after a single act of unprotected sex.
Effectiveness declines as the interval between intercourse and the start of treatment increases.
In the first 24 hours after intercourse, Plan B can prevent 95 percent of expected pregnancies. No serious complications have been associated with Plan B. Used as directed, Plan B is safe for most women. Plan B should not be used by women who are already pregnant, who have undiagnosed abnormal genital bleeding, or who are hypersensitive to any ingredient in the product. While no studies have specifically ruled out the possibility of teratogenic effects, there are no biomedical or scientific data to suggest that there would be an increased risk of birth defects if Plan B fails or if a woman who is already pregnant takes Plan B. Studies involving women who have inadvertently taken combined oral contraceptives containing levonorgestrel during early pregnancy suggest that these drugs do not have an adverse effect on the fetus. Information and links in this press release were accurate as of the date near the title of the article.