A Study to Compare 3 Doses of a Hormonal Intra-uterine Device Containing Levonorgestrel and Indomethacin With a Hormonal Intra-uterine Device Containing Only Levonorgestrel to Assess the Effect and Safety of the Combined Components

Inclusion Criteria: * Agreement to use an acceptable non-hormonal method of contraception (i.e. male or female condom with or without spermicide; cap, diaphragm or sponge with spermicide) when sexually active. This applies during the pre-treatment cycle and directly following the treatment period until the end of the follow-up period. This is not required if safe contraception is achieved by a permanent method, such as bilateral fallopian tube blockage of the subject or vasectomy of the partner(s). * Age at screening: 18-45 years inclusive * Body mass index (BMI) at screening: ≥ 18 and ≤ 32 kg/m² * No clinically relevant abnormal findings in the pre-treatment endometrial biopsy * Adequate venous access (for frequent blood sampling) Exclusion Criteria: * Menstrual disorders with unknown reason (not e.g. oligomenorrhea, hypomenorrhea amenorrhea due to hormonal treatment; not irregularities occurring during menarche). In case it is suspected that the woman is peri-menopausal, she should be excluded. * Use of short-acting hormonal contraceptives/preparations containing sex hormones (oral, transdermal, intravaginal, IUS) during the pretreatment cycle * Use of long-acting preparations containing sex hormones within the 40 weeks before the first screening examination (any long-acting injectable or implant) * History of known or presence of suspected or known malignant tumors, especially any breast cancer, cervical carcinoma in situ or other progestin-sensitive cancer * History of skin reactions, or other allergic-type reactions or known hypersensitivity reactions after taking aspirin, IND or other NSAIDs or to LNG, or any excipients of the IUSs * Regular use of corticosteroids, irrespective of route of administration * Known asthma bronchiale and aspirin-sensitive asthma * Current or recurrent pelvic inflammatory disease * Abnormal cervical smear within the last 6 month prior to screening * Acute genital infection * Known current thyroid disorders which require treatment (subjects with an euthyroid struma who do not need any treatment can participate)