healthy women aged 16-20, who were sexually active and at risk of pregnancy, had regular menstrual cycles and at least one normal menstrual cycle, body weight less than 90 kg and no use of any other steroid hormonal therapy at least 3 months before beginning the present study. Exclusion criteria included pregnancy and lactation, any acute or chronic liver disease, history of significant cardiovascular, hepatic, renal or thromboembolic disease, hypertension > 140/90 mmHg, metabolic disturbance or any malignant tumor, history or presence of dermal hypersensitivity, undiagnosed abnormal uterine bleeding, active cigarette smoking,and alcohol or drug abuse.