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  2. Age and female fertility - Wikipedia

    en.wikipedia.org/wiki/Age_and_female_fertility

    The average age of a girl's first period is 12 to 13 (12.5 years in the United States, [6] 12.72 in Canada, [7] 12.9 in the UK [8]) but, in postmenarchal girls, about 80% of the cycles are anovulatory in the first year after menarche, which declines to 50% in the third year, and to 10% by the sixth. [9]

  3. Menstrual cycle - Wikipedia

    en.wikipedia.org/wiki/Menstrual_cycle

    Menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the ...

  4. Menstruation - Wikipedia

    en.wikipedia.org/wiki/Menstruation

    Diagram illustrating how the uterus lining builds up and breaks down during the menstrual cycle Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone ...

  5. Menarche - Wikipedia

    en.wikipedia.org/wiki/Menarche

    In very rare instances, menarche may occur at an unusually early age, preceding thelarche and other signs of puberty. This is termed isolated premature menarche, but other causes of vaginal bleeding must be investigated and excluded. [16] Isolated premature menarche is rarely the first manifestation of precocious puberty. [citation needed]

  6. Teenage pregnancy - Wikipedia

    en.wikipedia.org/wiki/Teenage_pregnancy

    The definition of teenage pregnancy includes those who are legally considered adults in their country. [2] The World Health Organization defines adolescence as the period between the ages of 10 and 19 years. [6] Pregnancy can occur with sexual intercourse after the start of ovulation, which can happen before the first menstrual period (menarche ...

  7. Delayed puberty - Wikipedia

    en.wikipedia.org/wiki/Delayed_puberty

    Puberty is considered delayed when the child has not begun puberty when two standard deviations or about 95% of children from similar backgrounds have. [7] [8] [9]In North American girls, puberty is considered delayed when breast development has not begun by age 13, when they have not started menstruating by age 15, [2] and when there is no increased growth rate. [8]

  8. Amenorrhea - Wikipedia

    en.wikipedia.org/wiki/Amenorrhea

    Primary amenorrhea is defined as an absence of secondary sexual characteristics by age 13 with no menarche or normal secondary sexual characteristics but no menarche by 15 years of age. [3] It may be caused by developmental problems, such as the congenital absence of the uterus, failure of the ovary to receive or maintain egg cells , or delay ...

  9. Menstruation celebration - Wikipedia

    en.wikipedia.org/wiki/Menstruation_celebration

    Most girls get their first menstrual cycle between 12 and 13 years old, according to The American College of Obstetricians and Gynecologists. The age of menstruation onset is slightly younger for Black girls due to health disparities, increased material hardship, and levels of stress. For Black girls, the first moon party is a rite of passage ...