Participants in the study will use mifepristone 50 mg once-a-week for one year as a contraceptive. With this, we want to confirm that the chances of getting pregnant while using this contraceptive are very small. We also want to demonstrate that the use of mifepristone is safe, and it does not lead to any severe health problems. We expect fewer side effects compared to other frequently used contraceptives with hormones. Mifepristone does not contain these hormones. It is important to know how people experience that use of one tablet a week.

Mifepristone 50 mg, a progesterone receptor modulator, is a proven safe emergency contraceptive and a promising new weekly contraceptive. As mifepristone does not contain estrogens or progestogens, we anticipate users will not experience the undesirable side effects and health risks of current hormonal contraceptives. Furthermore, pills are a highly desired formulation approach and a weekly regimen instead of daily administration will likely contribute to a high acceptability and adherence among users. Based on promising early stage clinical data, we expect the use of weekly mifepristone 50 mg as a contraceptive will be safe, effective, and acceptable.

Inclusion Criteria:

1. Age 18-35 at the moment of signing the informed consent.
2. In case of 30 years or older, prior HPV or pap-test.
3. Understand and speak Dutch or English.
4. Willing to use mifepristone as the only method of contraception for 12 months.
5. Able to take oral medication and willing to adhere to the study protocol.
6. Have unprotected vaginal heterosexual intercourse with a non-sterilized partner at least once a month.
7. BMI < 35 kg/m2.
8. Willing to fill in a daily diary on the smartphone or computer and five times an on-line questionnaire.
9. Able to participate in the scheduled visits and comply with the study protocol.
10. Provide informed consent about participating in study and provide permission to request medical data in the event of complications or pregnancy.
11. In case of not using hormonal contraceptives, menstrual cycle of 21-35 days.
12. In case of Depo-Provera (3 month injectable) at least 3 cycles of 21-35 days after stop.
13. In case of necessary progesterone treatment, be willing to use condoms temporarily.

Exclusion Criteria:

1. Currently pregnant or breast-feeding.
2. Desire to become pregnant within the following 12 months.
3. Signs of current endometritis, incomplete abortion after miscarriage or induced abortion, or retained pla-cental rests after delivery.
4. Undiagnosed post-coital bleeding or unscheduled bleeding (spotting with COC, patch, vaginal ring, hormo-nal IUD, implant allowed).
5. Known subfertility or history of ectopic pregnancy, unless intra-uterine pregnancy afterwards, or grade 3-4 endometriosis proven by laparoscopy.
6. History of gastric reduction or gastric bypass or use of weight-loss medicines.
7. Previous or current liver illness, previous or current infection affecting the liver (such as Hepatitis) or mod-erately abnormal liver enzymes at screening (ALAT, ASAT or bilirubin > 2 ULN).
8. Current or previous cancer or DCIS.
9. Family history of endometrial cancer, except BRCA genome mutation.
10. Known allergy to mifepristone.
11. Using non-dermal corticosteroids or any drugs that may interact with mifepristone. These include hydan-toins (e.g. phenytoin), barbiturates (e.g. phenobarbital), primidone, carbamazepine, rifampicin, oxcarbaze-pine, topiramate, rifabutin, felbamate, ritonavir, nelfinavir, griseofulvin and products containing St. John's wort (Hypericum perforatum).
12. Treatment with another investigational drug or participating in another intervention study, unless the prin-cipal investigators agree.
13. Undiagnosed reason for severe anemia or increased creatinine.
14. Abnormal previous PAP smear > pap II without colposcopic evaluation or untreated HSIL.
15. Systolic blood pressure ≥ 180 mmHg and/or diastolic ≥ 110 mmHg (hypertension with medical treatment allowed).
16. Intracavitary abnormalities on vaginal ultrasound, including intracavitary polyps or myomas, endometrium > 15 mm, or an obvious sign of hydrosalpinx.
17. Previous participation in the WOMEN&More trial.