Emergency contraception (brand name Plan B) should be taken within 72 hours of unprotected penis-to-vagina (vaginal) sex. If taken within 72 hours it is 75-89% effective. These two pills help prevent pregnancy. They are NOT the abortion pill. If a pregnancy already exists, the emergency contraception will not hurt the pregnancy. If you are under the age of 17 you will need a prescription for Plan B. You can get a prescription at your doctor's office, family planning clinic, or at CCHD Teen Clinic. A male or female 17 and older can get Plan B without a prescription.