Inclusion Criteria:  Women aged between 18 and 40 years. Women who are not lactating. Non-pregnant women Women have regular menstrual cycles every 21-35 days with a typical cycle length variation of no more than 5 days. Women who will ESI only for pregnancy prevention for at least 12 months. Have not any medical or gynecologic problems.  Exclusion Criteria:  Women with any contraindications for progesterone-only contraception in accordance with WHO eligibility criteria. Refuse participation in the study.