Information on periods

Wellbeing of Women funds vital medical research on periods.

Period problems are very common and can seriously affect a woman’s quality of life, causing pain, stress, embarrassment, anaemia and exhaustion. If there has been an unexplainable change in your usual cycle or you are suffering extremely heavy or painful periods, you should make an appointment to see your GP.


Menstruation, otherwise known as a period, is the shedding of the inner lining of the uterus through the vagina, which occurs roughly once a month. The first period usually begins between the ages of twelve and fifteen, and is known as menarche. However, periods can start as early as the age of eight, and still be considered normal. If a woman’s first period hasn’t appeared by the age of 15, this is known as amenorrhea.

Women generally stop menstruating between the ages of 50 and 55, with the average age being 51. This is known as the menopause – one year without a period.

Why do we have a menstrual cycle?

A woman is born with all her eggs already in her ovaries. When she starts her periods, one egg per menstrual cycle develops and is released. Once it has been released (ovulation), the egg lives for 24 hours.

If sperm meets the egg during this 24-hour period, it will fertilise the egg. Sperm can survive for up to seven days after sex, which means that if intercourse takes place prior to ovulation a woman can still get pregnant.

If the egg doesn’t get fertilised, it gets reabsorbed in the body. The inner lining of the womb, which will have gradually been building up since ovulation in order to support a pregnancy should it arise, is shed through the vagina. Therefore, we have periods because we release an egg each month, and this egg doesn’t usually get fertilised.

What actually goes on in the body during the menstrual cycle?

The menstrual cycle is controlled entirely by hormones. The process each month starts in the brain, when the hypothalamus produces a hormone called gonadotrophin-releasing hormone (GnRh). This travels to the pituitary gland and tells it to release follicle-stimulating hormone (FSH), which makes the eggs on your ovaries start ripening in preparation for release.

Between three and 30 follicles (sacs that contain eggs) start maturing in the ovaries, one of which (occasionally two or more) will grow faster than the others.

At the same time, FSH also tells the ovaries to produce oestrogen, which encourages the eggs to mature and starts the thickening of the lining of the womb so that it’s ready to support a pregnancy if the egg gets fertilised. Oestrogen also acts on the vaginal mucus, making it thin and clear – and easy for a sperm to swim up to the Fallopian tubes.

As the oestrogen levels rise, FSH levels falls slightly, but then rises again, along with a huge surge of luteinising hormone (LH), which is also produced in your pituitary gland. It is this surge of LH that triggers ovulation, where the most mature egg bursts out of its sac and away from the ovary and enters the Fallopian tube.

After ovulation, the now empty follicle becomes a corpus luteum, a small yellow mass of cells. This mass starts producing progesterone, which affects the mucus in the cervix to make it thicker and stickier, and therefore impenetrable to sperm.

Progesterone also makes the womb lining thicker and spongy by increasing blood supply to it, ensuring it is ready to receive a fertilised egg for implantation. The pituitary gland stops producing FSH to ensure that no more eggs mature in your ovaries.

If the egg is fertilised, it will travel down the Fallopian tube and embed itself in the lining of the womb. Progesterone levels will remain high and you will begin to feel the early signs of pregnancy. If the egg isn’t fertilised, or doesn’t successfully implant in the lining of the womb, it will begin disintegrating and the corpus luteum will shrink. Because of this, oestrogen and progesterone levels will go back down, and the womb lining will produce prostaglandins.

These chemicals will cause the lining of the womb to break up and start contracting, shedding itself and coming out through the vagina as period blood.

What is a normal period like?

Your period can last between three and eight days, with bleeding heaviest during the first two. Your period blood will be red when your period is at its heaviest, but may be pink, brown, or even black on lighter days.

Most women lose between 30 and 72 ml of blood (between five and 12 teaspoons) during their period, but those who have very heavy periods will lose more than this.

Heavy bleeding

If you lose an excessive amount of blood during your period, this is known as menorrhagia. It can sometimes occur alongside other symptoms, such as period pain, and can be entirely harmless.

It’s difficult to determine a precise definition of heavy bleeding because what is normal and healthy for one woman may cause another a lot of distress. Generally, heavy bleeding is considered to be 60ml or more in each cycle, given that the average amount of blood loss is 30 to 40ml.

If you feel like you’re using an unusually high number of tampons or pads, you bleed through your clothes or bedding, or you need to use tampons and towels together, this suggests you are bleeding a lot. If you think your periods are abnormally heavy, or if they are causing you distress, go and visit your doctor to get checked out.

Several conditions can cause heavy bleeding, including polycystic ovary syndrome (PCOS), pelvic inflammatory disease (PID), fibroids, and endometriosis. Very rarely, heavy bleeding can be caused by cancer of the womb.

Period pain

Period pain is very common and very normal, with most women experiencing it at some point in their lives. It normally involves painful muscle cramps in the tummy, and occasionally these can spread to the back and thighs. Sometimes the pain comes in spasms, and other times it is constant and dull, and it can vary with each monthly period.

The pain is caused by the muscular wall of the womb contracting. Mild contractions pass through your womb continually, but most women can’t feel them. During your period, the wall of the womb contracts with more force to encourage the womb lining to shed.

As these contractions occur, the blood vessels lining your womb get compressed, which temporarily cuts off their bloody supply, and therefore their oxygen supply. Without oxygen, the tissues in your womb release chemicals that trigger pain.

To make matters worse, the body produces prostaglandins at the same time as it releases pain-triggering chemicals – and these prostaglandins encourage the womb muscles to contract more, which increases pain levels further.

Occasionally, period pain can be caused by an underlying medical condition, in which case it is often referred to as “secondary dysmenorrhoea”. If you notice a change in your normal pattern of pain, or if you pain is too severe to deal with, go and visit your GP.

Stopped or missed periods

There are lots of reasons why you might miss a period, or even why your period might stop altogether. The most common reasons for a missed period include pregnancy, stress, sudden weight loss, being overweight, extreme over-exercising, certain types of contraception, reaching the menopause, or PCOS.

There are some serious conditions which can cause your periods to stop including heart disease or uncontrolled diabetes. If your periods stop for three consecutive months you should go and see a doctor and get it checked out.

If your periods have always been regular, but you start missing periods or they become erratic or irregular, you should also see a doctor to ensure there is nothing serious going on.

This has been written by The Femedic, an educational website that deals specifically with areas of women’s health considered taboo.

The Femedic is proud to partner with Wellbeing of Women to produce educational content and resources, and to raise awareness of women’s health issues.

Heavy Periods

1 in 5 (20%) of women experience unusually heavy periods. Menorrhagia, heavy periods that occur over a number of cycles, is one of the most common gynaecological complaints. Some women experience it from a young age, but many women only experience it after the ages of 30 or 40 e.g. after stopping the pill or after having children. Fortunately, it’s not a life-threatening condition, but excessive loss of blood, prolonged and irregular periods and bleeding between periods can have a dramatic impact on your life. Menorrhagia is recognised as a medical condition and it is treatable. Your GP can discuss the available treatment options with you however you can also find some excellent information on