Contraception

Inclusion Criteria

-  Healthy female subject.
 - Willingness to use non-hormonal methods of contraception during the study. 
 - This applies during the cycle preceding the pre-treatment cycle until the end of follow-up.
 - Age at screening: 18–40 years inclusive.
 - Body mass index (BMI) at screening: ≥ 18 and ≤ 32 kg/m².
 - History of regular cyclic menstrual periods.
 - No clinically relevant abnormal findings in the pre-treatment endometrial biopsy.

Exclusion Criteria

-Incompletely cured pre-existing diseases for which it can be assumed that the absorption, distribution, metabolism, elimination and effects of the study drugs will not be normal.
 - Any presence or history of known or suspected malignant tumors, especially any known or suspected breast cancer or other progestin-sensitive cancer.
 - Any presence or history of known or suspected benign tumors of the liver or of the pituitary or adrenal gland.
 - Amenorrhea (with unknown reason, not amenorrhea due to hormonal treatment) for more than 3 months within the 6 months before the first screening examination.
 - Use of short-acting preparations containing sex hormones during the cycle preceding the pre-treatment cycle (oral, transdermal, intravaginal, IUS).
 - Use of long-acting preparations containing sex hormones within the 40 weeks before the first screening examination (any long-acting injectable or implant).
Clinically relevant findings in the physical examination (e.g. pronounced varicosis, thrombophlebitis, and evidence of peripheral circulatory disturbances).
Menstrual disorders with suspicion of ovarian failure (e.g., oligomenorrhea, amenorrhea, hypomenorrhea).
 - Known bleeding irregularities
 - Current or recurrent pelvic inflammatory disease, including pelvic inflammatory disease within 6 month prior to the insertion of the IUS and any active sexually transmitted disease.
 - Anovulatory pre-treatment cycle (ovulation has to be observed by day 27 at the latest).
 - Positive result of urine pregnancy test.