The purpose of this study is to examine how different levels of physical activity impact the ovarian reserve during the pre-menopausal period

Two groups are included:

1. The study group: women between 20-35 years of age who practice high level of physical activity, as defined by International Physical Activity Questionnaire , for the past 3 years
2. The control group: women between 20-35 years of age who practice low level of physical activity, as defined by International Physical Activity Questionnaire , for the past 3 years

Women who meet the criteria for inclusion for will be recruited to the study after signing a consent form. Recruitment will be done through sport centers. The control group will include women being examined in gynecologic emergency department, after signing a consent form, if they meet the control group's inclusion criteria. These women will be asked to fulfill the International Physical Activity Questionnaire and additional questionnaire regarding relevant demographic and medical information (see below). Blood samples to anti-mullerian hormone , leptin, and hormonal profile will be obtained in day 3 of menstruation. Ultrasound will be performed to measure Antral Follicular count and ovarian blood flow.

Data collection:

1. Demographic information on age, weight, height, BMI, marital status
2. Medical information regarding chronic diseases and medications
3. Obstetrical history
4. Information regarding physical activities in the version of International Physical Activity Questionnaire .
5. Information about menstrual behavior: irregularity (yes/no) frequency (less than 21 days between 21-35 days, over 35 days), menstrual duration (less than 3 days 3-7 days, or over 7 days) bleeding amount according to the number of pads per day (up to 1, 2, 4 or 5 pads).
6. Hormonal profile - Follicle-stimulating hormone , Luteinizing hormone , progesterone, Estradiol, Thyroid-stimulating hormone .
7. Antral Follicle Count, Anti-mullerian hormone
8. Leptin levels -reflecting metabolic changes.

Inclusion Criteria:

Study group:

1. Women between 20-35 years of age who practice high level of physical activity, as defined by International Physical Activity Questionnaire, for the past 3 years
2. BMI 18-25
3. Regular menstruation

Control group:

1. Women between 20-35 years of age who practice low level of physical activity, as defined by International Physical Activity Questionnaire, for the past 3 years
2. BMI 18-25
3. Regular menstruation

Exclusion Criteria:

1. Polycystic ovary syndrome 2. Endometriosis 3. Diabetes 4. Hyper/hypothyroidism 5. BMI>25, BMI<18 6. Active or past eating disorder

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Control group - Recruitment will be done through Gynocologis tEmergency Experimental group - Recruitment will be done through sport centers