Effects of Obesity on Pharmacokinetics of the Levonorgestrel Emergency Contraceptive Pill

Inclusion Criteria: * Women between ages 18-35 years * Regular menstrual cycles (24-35 days) for the past 2 months * Ovulatory at defined by midluteal progesterone level \>3 ng/mL (Day 18-25) * Belongs to one of the following categories: normal weight (BMI = 18.5-24.9 kg/m2), obese (BMI = 30-39.9 kg/m2) or extremely obese (BMI ≥ 40 kg/m2) * Participant has no intention of or desire to conceive (e.g., active attempt to become pregnant or in vitro fertilization) for the duration of the study * Participant agrees to consistently use an effective method of nonhormonal contraception throughout the duration of study, which could include: condoms (male or female) with or without a spermicidal agent, diaphragm or cervical cap with spermicide, non-hormonal intra-uterine devise (IUD), or sterilization. * Able to give informed consent Exclusion Criteria: * • Known renal or liver disease * Known pituitary disorder * Known adrenal disorder * Known thyroid disorder * Use of medication known to alter the cytochrome P450 system * Use of depot-medroxyprogesterone acetate in the previous 6 months or any other hormonal contraceptive in the previous 3 months * Currently breastfeeding * Pregnant * Pregnancy in the prior month * Known allergy to medication * Other specific contraindications to LNG EC