Women's Health
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    Your Menstrual Cycle Explained

    Periods. They affect 50% of the population (give or take) and yet it’s a subject that we continue to avoid talking about and this can lead to a lot of women not fully understanding their bodies. Right from when a woman gets her first period, she may be embarrassed to tell her parents. Fast forward to adult life and you’ll find women slipping tampons and sanitary pads up their sleeves or in their pockets before going to the toilet, and avoiding the discussion of periods within a hundred mile radius of any male. It’s time to break down the taboo and look at the facts.

    Key Takeaways

    Understanding the Menstrual Cycle:

    The menstrual cycle, controlled by hormones like oestrogen and progesterone, typically lasts 28 days. Oestrogen helps release an egg, while progesterone thickens the uterus lining in preparation for a potential pregnancy. If the egg is not fertilised, the uterus sheds its lining, causing a period, which usually lasts about 7 days.

    Causes and Symptoms of Periods:

    Periods result from the shedding of the uterus lining when a fertilised egg is not present. Symptoms vary among women, ranging from mild to severe cramps, mood swings, headaches, and food cravings. The average blood loss during a period is about 5 teaspoons, even for those with heavy periods.

    Ovulation and Fertility:

    Ovulation occurs around day 14 of the menstrual cycle when an egg is released from the ovaries. The egg travels through the fallopian tubes to the uterus, where it can be fertilised by sperm. The fertile window lasts about 7 days. Women typically continue ovulating until around age 50, when menopause begins, leading to the end of menstrual cycles and associated symptoms like hot flashes and mood changes.

    How does the menstrual cycle work?

    Hormonal changes during your teenage years

    Your menstrual cycle is very much controlled by hormones and your body begins to produce these when you hit puberty; typically between the ages of 8 and 13 for girls and 9 and 14 for boys. This slight gap in hitting puberty explains why girls are often taller than boys at this age. As well as a growth spurt though, a girl hitting puberty signals the start of her reproductive years. Most girls get their first period between the ages of 10 and 15, with around 12 years old being the average.

    You're born with a finite number of eggs

    Your reproductive years are controlled by the number of eggs you have in your body, as current knowledge says that you are born with your total amount, and do not produce any more after this point; you simply release them until they are gone. The egg cells lie dormant in small pockets called follicles, until your hormones kick in and cause the follicles to mature into egg cells.

    Oestrogen and Progesterone

    The hormones involved in your menstrual cycle are oestrogen and progesterone, and your cycle is based on a 28 day period. Oestrogen is the hormone that aids in the release of an egg, while progesterone is responsible for thickening the lining of the uterus, in preparation for said egg.

    Oestrogen levels slowly increase during your period and in the days afterwards, and then sharply spikes as an egg is released. This then sharply drops again after ovulation is complete and then increases to a similar pattern as progesterone does from approximately day 16 to day 28 of your cycle. Progesterone levels remain steady for the first half of your menstrual cycle and then begin to creep up once you hit ovulation (usually at day 14). This continues to steadily increase, peaks at day 21 and then slowly decreases again until day 28, remaining steady again until your next ovulation.

    A calendar with menstruation cycles marked on it

    What causes periods?

    Your period is thought of as the beginning of your menstrual cycle and usually counts for days 1 to 7 (the length of a woman’s period varies from person to person but 7 days is fairly standard). Along with the duration of your period, every woman will experience the severity and other associated symptoms differently.

    Some women suffer from very painful, heavy periods, while others barely notice theirs. If you do suffer with premenstrual symptoms (otherwise known as PMS) then you may notice headaches, mood swings, bad skin, and food cravings. The most common of all though is stomach cramps and these are caused because of the menstrual cycle process.

    While your period may look like blood, the fluid that comes out of your body is actually your uterus lining.

    • When ovulation occurs, your progesterone levels start to pick up and this causes the lining of your uterus to thicken in preparation to house and nourish a growing foetus. However, if the egg is not fertilised then it will die and your body will no longer have a need for the thicker uterus lining.

    • To get rid of the lining, your uterus starts to contract and relax sporadically. This motion helps to shake away the lining and shed it, but it also causes the stomach cramps.

    Although the blood that appears on a pad or tampon may look like a lot, most women only lose about 5 teaspoons worth per period. Even women who suffer from particularly heavy periods are only likely to be secreting 10 teaspoons worth, so although the blood can seem like an alarming amount, it’s actually not as much as it may seem.

    A graph of a typical ovulation cycle

    What is ovulation?

    Ovulation is a term used to describe the process of an egg being released, ready to be fertilised. As mentioned, a woman starts her life with all of her eggs and then releases one a month once she reaches reproductive age.

    As your oestrogen levels peak (at around day 14 of your menstrual cycle), an egg is released from your ovaries and travels along the fallopian tubes, into your uterus. If it reaches the uterus and is not fertilised by a sperm then the egg will die and will leave the body through your vagina. The process of the egg leaving the ovaries is what begins ovulation and the egg entering the uterus is what ends it,.

    Because of the time that ovulation takes, combined with the lifetime of sperm, there is usually a 7 day window when a woman can become pregnant. When a woman does become pregnant, she does not have periods or ovulate for the 9 months that the baby is growing inside of her, but usually commences the process again approximately 3 weeks after giving birth.

    Most women continue with this monthly cycle until around the age of 50, at which point she runs out of eggs and the process either slows down erratically or stops completely. The lack of menstruation then leads to a lack of hormones, which can cause symptoms such as hot flashes, mood changes and alterations to libido. This process is known as the menopause and usually lasts for 4 years.

    If your menstrual cycle is coming at an inconvenient time, you may be interested in trying a period delay medicine. One such type of medicine which can delay your period for up to 17 days is Norethisterone. This is a prescription-only medication. If you do not have a prescription, you can order it today from UK Meds, using our prescription service.

    Medically Reviewed by:
    Dr. Alexis Missick MBChB. MRCGP
    GMC reference no: 7151419

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