Obese women are significantly more likely than their normal BMI counterparts to experience failure of orally-dosed emergency contraceptives. The PI's preliminary data provides evidence for testing a dose escalation strategy in an effort to provide improved efficacy from orally-dosed emergency contraceptives in obese women. The overall project will be focused on both levonorgestrel (LNG) - and ulipristal acetate-containing emergency contraception but this protocol registration is for the LNG aspect of the study procedures.

Emergency contraception (EC) provides a woman with an additional line of defense against unintended pregnancy following an act of unprotected intercourse. Orally-dosed EC works by delaying ovulation and reduces the risk of pregnancy for a single act of unprotected intercourse by 50-70%. Unfortunately, obese women are significantly more likely than their normal BMI counterparts to experience failure of orally-dosed EC and in some instances EC is equivalent to placebo.

The PI's preliminary data provides evidence for testing a dose escalation strategy in an effort to provide improved efficacy from orally-dosed EC in obese women. The hypothesis is that increasing the dose of orally-dosed EC agents will normalize the pharmacokinetics resulting in the expected treatment effect (delay in follicle rupture) in obese women. In the overall proposal, the investigators plan to perform detailed pharmacokinetic and pharmacodynamic studies of ulipristal acetate-based EC in obese women and expand upon the preliminary findings of levonorgestrel-based EC. This protocol registration is for the LNG aspect of the study procedures focused on the pharmacodynamics of LNG dose escalation

Inclusion Criteria:

• Generally health women
• Aged 18-35 years old
• Regular menses (every 21-35 days) experiencing an ovulatory screening cycle with a progesterone level of 3ng/ml or greater.
• Subjects must have a BMI of >30 kg/m2 and weigh at least 80 kg or more.

Exclusion Criteria:

• Metabolic disorders including uncontrolled thyroid dysfunction and Polycystic Ovarian Syndrome
• Impaired liver or renal function
• Actively seeking or involved in a weight loss program (must be weight stable) pregnancy, breastfeeding, or seeking pregnancy
• Recent (within last 8 weeks) use of hormonal contraception
• Current use of drugs that interfere with metabolism of sex steroids
• Smokers.

PI acknowledges willingness to share data and materials with other investigators through established means. Data will be shared with collaborators as soon as available; with other scientists before publication if the work to be done is different from the PI's purposes; with local colleagues at seminars and talks including the yearly university-wide research-in-progress seminar; and with the scientific community at large by posters and presentations at local, regional, national, and international scientific meetings. Data will be presented via publication to the widest audience possible.

Transfer of resources is subject to the acceptance of a Materials Transfer Agreement as required by policy at OHSU.

OHSU complies with NIH policy on Sharing Research Data and on Sharing Model Organisms.

All enrolled participants completed the study and were part of the analysis.

90 days