Question: Emergency contraception was not available to the woman in the interview when she was in college nearly 30 years ago. How are emergency contraceptive pills (ECPs) taken 3 to 5 days after unprotected intercourse used to prevent pregnancy? Need Assignment Help? ECPs inhibit ovulation or fertilization or block implantation of a fertilized egg. ECPs are used by women who cannot tolerate the side effects of regular birth control pills. ECPs are a method of sterilization used to prevent future pregnancies. ECPs are a type of medication abortion that must be performed early in the pregnancy.