A mere one percent of women has ever used emergency contraception. The reasons for this vary, but Dr. Purdon noted that some doctors may assume their patient is not a candidate for EC, and many women either don't know to ask about EC or believe they would never need it. Both assumptions are wrong, according to Dr. Purdon. Half of the 3 million unintended pregnancies each year occur to women who experienced a contraceptive failure. The timing of ovulation is unpredictable and sperm can live for several days inside a woman's reproductive tract.
Emergency contraception can prevent pregnancy in several ways.
It may prevent ovulation, fertilization, or implantation of the egg in the uterus. All are necessary stages for pregnancy to occur. However, the window of time for EC to work is short. The bottom line is that women need to begin emergency contraception within 72 hours of unprotected sex. For four decades, doctors have known about the ability to prevent pregnancy by providing a concentrated dosage of birth control pills shortly after unprotected sex.