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The menstrual cycle
Reviewed by Dr Philip Owen, consultant obstetrician and gynaecologist and Dr Jeni Worden, GP
What is menstruation?
Menstruation - having periods - is part of the female reproductive cycle that starts when girls become sexually mature at the time of puberty.
During a menstrual period, a woman bleeds from her uterus (womb) via the vagina. This lasts anything from three to seven days. Each period commences approximately every 28 days if the woman does not become pregnant during a given cycle.
Why do women menstruate?
Menstruation is a very complicated process involving many different hormones, the woman's sex organs and the brain.
A woman's internal sex organs consist of two ovaries, the Fallopian tubes, the uterus (womb) and the vagina. The ovaries contain the eggs with which the woman is born and, during each period, a single egg will usually ripen and mature due to the action of hormones circulating in the bloodstream.
When the egg is mature it bursts from the ovary and drifts through the Fallopian tube down into the uterus. The lining of the uterus - the endometrium - has been thickened by the action of hormones and made ready to receive the fertilised egg.
If the egg is fertilized and the woman becomes pregnant, it will fasten itself onto the endometrium. If the egg is not fertilized, however, resultant hormonal changes cause the endometrium to slip away and menstruation begins.
Menstrual discharge is composed of the endometrium itself, together with a little fresh blood caused by the breaking of very fine blood vessels within the endometrium as it detaches itself from the inside of the uterus.
The amount of blood lost due to the normal monthly period is usually less than 80ml.
When does menstruation begin?
These days, girls begin to menstruate when they are about 10 to 14 years-old. The average age is approximately 12. Women will continue to menstruate until the age of 45 to 55, when menopause begins. A woman will have approximately 500 periods in her lifetime.
Can you feel ovulation?
Ovulation usually takes place roughly 14 days after the first day of the start of a period; however, the exact timing can vary greatly from woman to woman. Some women know when they are ovulating because they can feel a slight pain in their lower abdomen. Other women may bleed slightly in the middle of their cycle.
Vaginal discharge also changes at ovulation. It increases in amount and becomes more watery due to hormonal changes. This is one of the ways that women who wish to practice natural family planning (NFP) using the mucus test can find out whether it is safe to have sex or not.
Women who do not experience such symptoms during ovulation can find out when they are ovulating by taking their temperature. This will rise by 0.5 degrees Celsius when ovulation occurs. To measure temperature effectively, it must be taken at the same time every morning before getting out of bed.
Temperature readings taken from different parts of the body such as the mouth, under the arm, in the ear or in the rectum will all give a slightly different measurement. For this reason, it is important to choose one location and stick to it. When checking for temperature, rises can occur for a variety of reasons and, therefore, should not be used as the only method of detecting ovulation.
What influences menstruation?
As described above, menstruation is a very complex process involving many different hormones, the sexual organs and the nervous system.
First and foremost, hormones influence menstruation. If they are not in balance, the cycle will similarly be affected. If a woman's periods are very irregular, she can ask her doctor to measure the hormones in her blood to find out if her hormones are out of balance. This will give a rough indication as to whether there is a serious hormonal problem. However, since what is 'normal' varies greatly with regard to women's hormones, blood tests are not a particularly good measure of what can be considered much more subtle imbalances in a woman's cycle.
Weight also influences hormonal balance and menstruation. If a woman is underweight, her hormones will stop working properly and her periods might stop altogether. Recent research has also shown that obesity can throw hormones out of balance and make it harder for women to conceive. Stress also affects the hormones. Many women find that if they are worried about something, it can influence menstruation. In some cases, a woman's period might actually stop if she is very worried about whether she is pregnant.
Regular exercise and keeping fit and healthy can help regulate the menstrual cycle. On the other hand, exercising too much and overstressing the body can have a negative effect on the hormones to the extent that menstruation may cease.
What are the symptoms of painful periods?
The degree of discomfort experienced during menstruation varies from woman to woman. Some are never bothered by their periods, while others can be badly affected by unpleasant symptoms. These may include:
What can women do to relieve their symptoms?
There are several things that will help relieve discomfort:
Remember that it is always best to consult your doctor about your specific concerns.
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