The purpose of this study is to evaluate the contraceptive efficacy and safety of an oral contraceptive containing a combination of LNG 100mcg/EE 20mcg compared to LNG 150mcg/EE 30 mcg.

Inclusion Criteria:

• Healthy women,aged 20-35 years who wish to use a contraceptive.
• Women without reproductive system infection complications.
• Willingness to not use other forms of hormonal treatment.
• Three regular menstrual cycles before the study(21-35 days per cycle with 3-7 day's bleeding period, without amenorrhea or irregular bleeding).
• Signed informed consent prior to entry into the trial.

Exclusion Criteria:

• Any contraindication to the use of oral contraceptives.
• Vascular, metabolic, hepatic, renal, oncologic and other diseases.