Study to Evaluate 3 Dosages of Estetrol After 28 Days Administration in Healthy Postmenopausal Women

Inclusion Criteria: * Postmenopausal women not older than 70 years of age at the time of screening (menopause defined as ≥ 6 months amenorrhea with serum follicle-stimulating hormone \[FSH\] levels ≥ 40 IU/L and serum E2 \< 73 pmol/L). * Body mass index 18-30 kg/m2 inclusive. * Good physical and mental health, as judged by the Investigator, determined by medical history, physical examination, clinical laboratory values, vital signs, and electrocardiogram (ECG) recording. * Willing to give written informed consent. * Either \> 50 hot flushes per week or \< 10 hot flushes per week Exclusion Criteria: * Clinically significant abnormal results of routine hematology, serum biochemistry, urinalysis, and/or ECG in the opinion of the Investigator at screening. * Clinically significant abnormal mammogram (presence of any non-cystic mass) within one year before study start. * Clinically significant abnormalities of the uterus and/or ovaries detected by examination and/or ultrasound (non-physiological ovarian mass or significant uterine pathology or an endometrium greater than 6 mm). * A cervical smear with clinically relevant abnormal cytology within one year before study start. * Previous use of estrogen/progestogen within: * 6 months for depot preparations. * 8 weeks for oral preparations or progestogen containing intrauterine device (IUD). * 4 weeks for transdermal preparations. * Use of hormone containing implant at any time. * Contraindications for using steroids: * A history of, or existing thromboembolic, cardiovascular, or cerebrovascular disorder. * A history of, or existing conditions predisposing to, or being prodrome of, a thrombosis. * A known defect in the blood coagulation system (e.g. deficiencies in antithrombin-III \[AT-III\], protein C, S, and activated protein C \[APC\] resistance). * A medical history positive for the presence of more than one risk factor for vascular disease (e.g. dyslipoproteinemia; diabetes mellitus; hyperhomocysteinemia; systemic lupus erythematosus; chronic inflammatory bowel disease; smoking; venous thromboembolism in sibling or parent below the age of 50, or arterial disease in sibling or parent below the age of 30-35). * Hypertension, i.e. systolic blood pressure \>160 mm Hg and/or diastolic blood pressure \>100 mm Hg. * Disturbance of liver function: cholestatic jaundice, a history of jaundice in pregnancy or jaundice due to previous estrogen use, Rotor syndrome and Dubin-Johnson syndrome. * Known or suspected estrogen-dependent tumors or endometrial hyperplasia * Undiagnosed vaginal bleeding. * Porphyria. * A history during pregnancy or previous estrogen use of severe pruritus, herpes gestationis, or deterioration of otosclerosis. * Any medication (including over-the-counter \[OTC\] products) from 14 days prior to the day of dosing except for occasional non-steroidal anti-inflammatory drugs (NSAID; e.g. ibuprofen); paracetamol is not permitted. * Any enzyme affecting drugs from 30 days prior to Day 1 and the use of griseofulvin, primidone, oxcarbazepine, topiramate, felbamate, or herbal remedies containing hypericum perforatum (St. John's wort). * Presence of significant allergies or other serious diseases. * Smoking more than 10 cigarettes or equivalent per day. * Administration of investigational drugs within 3 months before start of study medication. * A history of (within 12 months) alcohol or drug abuse.