These disruptions are temporary, lasting only a day or two. ECPs prevent pregnancy by delaying or inhibiting ovulation, inhibiting fertilization or inhibiting implantation of a fertilized egg. If vomiting occurs within two hours of taking the pills, the pills may need to be taken again. Unplanned pregnancies in the United States occur among women who do not use any contraception as well as among women who were using contraception when they got pregnant. These latter women may have become pregnant because their contraceptive method failed.
Emergency contraception provides a back up.
Almost all women can safely use ECPs. Although some women at risk of stroke, heart disease, blood clots, or other cardiovascular problems should not use birth control pills on an ongoing basis, medical experts believe that short-term, emergency use of birth control pills does not carry the same risks. Ask your regular clinician about emergency contraception. Most women and men and many doctors in the United States do not know about emergency contraception. The primary reason is that no drug company has an emergency contraceptive product to market or advertise, so people cannot learn about emergency contraceptive pills through ads like they do other drugs.