Menstrual Cycle Explained

Our menstrual cycles are something which we women tend to take for granted unless they begin to cause us problems. At different stages of life, many women are bothered by irregular periods, heavy periods, or periods that don't come at all. In order to understand our bodies better and be able to communicate effectively with our doctors about menstrual issues, it's important for us to know how the menstrual cycle works when it's healthy and functioning normally. Many problems we perceive in our cycles may actually be natural phenomena that occur from time to time. On the other hand, many of us may be living with menstrual irregularities which do need to be investigated further.


Menarche is the name given to a girl's first period, which she may get at any time between the ages of eight and 15. When a baby girl is born, she already has all the eggs she will ever produce in storage inside her ovaries. The ovaries are two olive-sized reproductive glands located on each side of a female's lower abdomen. As a girl grows up and approaches puberty, her body starts to produce the sex hormones oestrogen and progesterone. These hormones encourage the eggs in the ovaries to mature. When the girl's body enters the stage of life in which she is physically capable of getting pregnant, she will experience her first menstrual cycle. This cycle will constantly repeat until she reaches menopause (probably when she is in her 50s).

The Cycle

Egg Maturation - While the eggs are maturing in the ovaries, the ovaries produce more oestrogen. This oestrogen encourages the growth of tissue which lines the uterus (also called the womb) and makes this lining ready to receive and nurture an egg, should an egg be fertilised. The uterus is the organ in which the fertilised egg settles and grows into a foetus. The opening of the uterus is called the cervix, and the cervix is connected to the vagina.

Egg Release - Once the eggs have had a chance to reach full maturity, another surge of hormones encourages one ovary to release a mature egg. This egg then travels down the fallopian tube connected to the ovary that produced the egg. This tube connects the ovaries to the uterus. When the egg gets into the fallopian tube, it has an approximate one- to three-day window in which to become fertilised.

Uterine Lining Disintegrates - While the egg is moving down the fallopian tube, if there are no sperm cells there to fertilise it, the levels of oestrogen and progesterone in the body begin to decrease. As this happens the lining of tissue in the uterus begins to break apart. Eventually, the egg itself will disintegrate too. Both the uterus lining and remains of the egg are flushed out via the vagina when the period begins.

Bleeding - the actual period usually lasts between five and eight days and is generally heaviest on the first two days of bleeding. The material flushed out of the body consists of the lining tissue and blood expelled from small blood vessels which break as the uterus lining detaches itself from the wall of the uterus.

Cycle Length - Each menstrual cycle is counted from the first day of bleeding of one period until, but not including, the first day of bleeding of the next period. For most women, the cycle lasts between 28 to 30 days approximately, but this varies from woman to woman


The fluctuations of hormones during the different stages of the menstrual cycle are responsible for menstrual symptoms, which most of us know as PMS, or premenstrual syndrome. PMS symptoms include: cramps before and during menstrual bleeding, headaches, pains in the back and abdomen, bloating, breast tenderness, mood swings, depression, etc. If you are troubled by any of your symptoms, you should make an appointment to discuss them with your doctor. Try keeping a record of the dates you start and stop bleeding each cycle and note any particularly bothersome symptoms. This will help your doctor to decide if you need some treatment. In many cases, PMS can be eased to some degree without using medication.

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