Etonogestrel (ENG) Implant Insertion for Emergency Contraception With Oral Levonorgestrel (LNG) vs Placebo

Inclusion Criteria: * Between 18-35 years old * Unprotected intercourse within 72 hours * Biologically capable of pregnancy (intact uterus without prior sterilization surgery * Fluent in English and/or Spanish * Have a regular menstrual cycle (21-35 days) * Known last menstrual period (+/- 3 days) * Working (cell) phone number * Willing to comply with the study requirements * Willing to abstain from any CYP3A4 inducer for 5 days Exclusion Criteria: * Current pregnancy (+urine pregnancy test in clinic) * Breastfeeding * Contraindication to ENG or LNG based on CDC MEC/SPR * Sterilization, hysterectomy, or has an IUD or contraceptive implant in place * Vaginal bleeding of unknown etiology * Previous use of EC in same cycle * Allergy to LNG or ENG * History of intolerance/ side effects with ENG Implant * Current (past 7 days) use of any CYP3A4 inducer * Plan to use any other steroid hormone in the next 4 weeks (testosterone, estrogen, progesterone) * Ended a pregnancy at or under 20 weeks gestational age within last 2 weeks * Ended a pregnancy over 20 weeks gestational age in last 6 weeks * Use of any injectable hormonal contraceptive (Depo-Provera) in the last 15 weeks * Use of any oral EC, contraceptive pills, patches, vaginal rings, or an IUD or Implant in the last 2 weeks