Plan B One-StepBy Mayo Clinic staff
Original Article: http://www.mayoclinic.com/health/medical/IM04402
Plan B One-Step
Plan B One-Step is a type of morning-after pill that can be used after unprotected sex to prevent pregnancy. Plan B One-Step contains the hormone levonorgestrel — a progestin — which can prevent ovulation, block fertilization or keep a fertilized egg from implanting in the uterus.