Progestin Only Pill Study

Group of women together

Progestin-only pills are oral birth control pills that have been used in the United States for several years. To be effective in preventing pregnancy, this kind of birth control pill is supposed to be taken every day at the same time, without delaying the intake for more than 3 hours. This type of pill prevents pregnancy by making the mucus of the cervix less penetrable for sperm at the time of ovulation and also by preventing ovulation. This trial aims to find out if taking the pill 6 hours late or not taking it for one day will affect the way it works.

Participation in this study lasts about 4.5 months and involves taking a progestin-only pill at the same time every morning for 3 months. There will be between 28-41 visits at OHSU that will include pelvic exams, transvaginal ultrasounds, blood draws, and questions about your health. These visits will occur twice a week or more frequently. Some visits may need to occur on weekends and holidays. Most visits will last about 30 minutes, but some visits may go for several hours or a full day.

If you are interested in helping us learn more, you are invited to contact us to see if you are eligible to participate.


  • You are between the ages of 18 and 35
  • You are not taking any hormones
  • You are not at risk for pregnancy (you are not sexually active, are in a same sex relationship, use a barrier method of birth control, have a partner with a vasectomy, or have had a tubal ligation yourself)
  • You have an intact uterus and both ovaries
  • You have regular menstrual cycles
  • You are in good general health
  • You have a BMI of less than 32


Qualified participants will receive all study related medical exams and laboratory services at no charge and will be compensated approximately $2,865 for their time and travel. The exact amount will depend on the number of visits completed.

Who do I contact for additional information?

To find out more information and to learn if you are qualified to participate, please fill out our online contact form, call the Women’s Health Research Unit's confidential recruitment line at 503-494-3666 or email us at .