Safety and Efficacy of CDB-2914 in Comparison to Levonorgestrel for Emergency Contraception

Inclusion Criteria: * women 16 or older in UK(except Northern Ireland) sites, 17 years or more in Northern Ireland (UK) and 18 years or more in Ireland and US * present within 120 hours of unprotected intercourse * regular menstrual cycles * No current use of hormonal contraception * Willing to not use hormonal methods of contraception until study completion * At least one complete menstrual cycle (2 menses) post miscarriage, delivery or abortion * For women who present more than 72 hours after intercourse, decline the insertion of an Intra Uterine Device for emergency contraception * Able to provide informed consent * Willing to abstain from further acts of unprotected intercourse until study completion Exclusion Criteria: * One or more acts of unprotected intercourse more than 120 hours * current or recent use of hormonal methods of contraception * currently pregnant or breastfeeding * tubal ligation or current use of IUD * Use of hormonal emergency contraception since last menstrual period * Current use of IUD * Tubal ligation * Partner with a vasectomy * Unsure about the date of the last menstrual period * Severe asthma insufficiently controlled by oral glucocorticoid * Hypersensitivity to the active substance levonorgestrel or any of the excipients of the drug products used in the study