• Question: why do we have a period once a month? and Why do we start so young?

    Asked by double N' to Craig, Laura, Partha, Saffron on 24 Jun 2015.
    • Photo: Laura Wales

      Laura Wales answered on 24 Jun 2015:

      Each month, the reproductive system repeats a regular pattern of events that are controlled by hormones (ie. rising and falling levels of oestrogen and progesterone). Rising hormone levels cause the ovary to develop an egg and release it (ovulation).

      After ovulation, in preparation for a potential pregnancy, hormones help the lining of the uterus thicken. Each month an egg is released by one of the ovaries and travels down the fallopian tube. If pregnancy doesn’t happen, the egg leaves the body with your menstrual flow. Oestrogen and progesterone levels fall and the lining of the uterus – comes away and leaves the body (the period). The entire cycle repeats and takes around a month, although it can vary from person to person (usually 28 – 35 days).

      Why do we start so young?
      I don’t think scientists have discovered the definite answer to this yet. Puberty happens much earlier than it used to so some scientists think it’s related to genetic and environmental factors. It could also be linked to diet and lifestyle – for example, girls who are overweight tend to start puberty earlier.

    • Photo: Saffron Whitehead

      Saffron Whitehead answered on 24 Jun 2015:

      A girls very first period is cal menarche and is due to the rising levels of hormones that occur during puberty when a girl begins to be sensitive to oestrogens. It takes a whille for regular period to become established but in most girls regular menstruation occurs regularly by the end of pubety or well before the completion of puberty.

      The reason women menstruate one a month is due to changing levels of hormones. During the first two weeks of a typical cycle the ovaries produce increasing amounts of oestrogen (oestradiol) as the follicle grows and the egg matures. Around mid cycle (typically day 14) the high levels of oestrogen cause an egg to be released from its follicle and the empty follicle forms what is known as a corpus luteum which secretes progesterone. High levels of oestrogens cause the lining of the womb (uterus) to grow and then the progesterone prepares the womb for implantation if pregnancy occurs in that cycle. If a woman doesn’t get pregnant then the corpus luteum (or yellow body) breaks down, it no longer secretes progesterone and this causes the lining of the womb to break away which causes the bleed of menstruation. The a new cycle begins again and another egg surrounded by its follicle begins to grow as does the lining of the womb. Very complicated and hope this makes sense.

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