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  • Menstruation
    • The menstrual cycle is a monthly cycle in which a woman’s uterus prepares for a fertilised egg to settle and grow into a baby.
      • Human fertility is controlled by four hormones and involves specialised cells. Chromosomes carry the genetic information for the formation of offspring including gender.
    • A woman is fertile, on average, between the ages of 12 to 50. During these fertile years, a recurring process - known as the menstrual cycle - takes place each month. This involves the lining of the uterus preparing for pregnancy.
      • The menstrual cycle usually lasts approximately 28 days. The first day of the cycle is the first day of a woman’s period (menstruation). The period – which usually lasts for 3-7 days - is made up of blood and the uterus lining. It passes out of the body through the vagina.
      • If pregnancy does not occur, the lining breaks down and the woman has a period. This is also known as menstruation.
    • After menstruation, the lining of the uterus builds up again (thickens) in preparation for a fertilised egg. Around day 14 of the cycle, an egg is released from a follicle in the ovaries - this is ovulation.
      • If this egg is fertilised and embeds itself in the thickened lining of the uterus, the lining is maintained and the woman becomes pregnant.
        • If a fertilised egg does not embed itself, the lining breaks down and menstruation occurs - and so the cycle repeats itself.
    • The menstrual cycle is controlled by the hormones oestrogen and progesterone.
      • Oestrogen is produced by the ovaries and makes the lining of the uterus repair itself and grow again after menstruation.
      • Progesterone is produced by the empty follicle in the ovary after the egg has been released. This hormone maintains the lining of the uterus during the second half of the menstrual cycle.
      • If a woman becomes pregnant the follicle continues to produce progesterone and a placenta is formed.
        • If pregnancy does not occur, then both hormone levels drop towards the end of the menstrual cycle, the lining breaks down and menstruation occurs.


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