The menstrual cycle is the series of changes which occur in the female body (usually each month) to prepare the body for pregnancy. The menstrual cycle is controlled by the rise and fall of several of the body’s hormones or chemical messengers that control certain body functions. If a woman does not become pregnant during the cycle, she will have a period. A cycle is counted from the first day of one period to the first day of the next period. Most women will have 450-500 periods in their life.
Menstruation is a woman’s monthly bleeding often called a period. When a woman menstruates, the body is shedding the lining of the uterus (womb or bag that holds the baby during pregnancy). This blood flows out of the opening (called the cervix) of the uterus, and then out of the body through the vagina.
The bleeding of a period can vary from very light to very heavy, and it can vary in colour from black/brown to bright red. Most women lose less than 80ml of blood (about four tablespoons in total) even though it often seems like more. The period contains blood, mucous and some cells from the lining of the uterus. Some small clots may be normal.
The period usually lasts from four to eight days. The flow of blood will change during the period; it is usually heavier for the first few days and then becomes lighter.
Many women will have some crampy discomfort/pain early in the period and for some women the pain can be quite significant, heat packs and simple pain relief medication may help. Some women may find that the oral contraceptive pill, Depo-provera, Implanon or Mirena intra-uterine contraceptive device may also help if they have heavy or painful periods. If pain is severe it is a good idea to see a doctor.
Some women may also have some slight spotting and/or pain, when they ovulate (release of an egg). This is usually about two weeks before the next period.
Pre-menstrual (before the period) symptoms can happen in the one to two weeks before a period.
Symptoms may include:
Normally these symptoms might be annoying but would not interfere with day to day activities. They usually settle when the period starts or in the first two to three days of the period.
In some women, symptoms can be so severe that their daily routine is affected and they cannot function properly. If this happens women should see their doctor or women’s health nurse.
The time when the menstrual cycle begins is called menarche (the first period). This usually happens when girls are about 12-13 years old, but can start as early as nine and as late as sixteen.
In the first two or three years after a girl’s period has started, the cycles can be irregular because ovulation does not always happen with each cycle. It takes the body a few years to develop a routine of releasing an egg and shedding the lining of the uterus every month.
The menstrual cycle ends with menopause (the final period). A woman has reached menopause when it is two years since her last cycle. The average age of menopause is 51 years but it may happen from 45-55 years. When a woman’s body is getting near the end of its reproductive life, the periods are often irregular like they were when they first started. This ‘winding down’ time before menopause is called perimenopause.
The length of the menstrual cycle is measured from the first day of one period to the first day of the next period. The length of the cycle can vary, for example in teenagers a cycle might be as long as 45 days, however by the 20-30s a cycle is usually between 21-38 days.
This video clip outlines the menstrual cycle, it is an animated version of what is written below.
Figure 1 shows a typical 28 day menstrual cycle from one period to the next. If the cycle is shorter or longer then ovulation may happen sooner or later.
Figure 1: The menstrual cycle
Hormones cause the now fully grown egg to burst out of the follicle and leave the ovary. This is called ovulation.
There are a variety of products available to use during a period including pads and tampons:
Pads: also known as sanitary pads or napkins. These are made of absorbent material and come in different thicknesses and shapes. If using pads causes irritation, women may need to use pads that are made from 100 per cent cotton and have no perfume. Pads usually need to be changed every 3-4 hours. Most pads are disposable but there are reusable/washable pads also available.
Tampons: are absorbent ‘plugs’ made of cotton, or a combination of cotton and a synthetic material and are available in different sizes. They can be used by all ages. Hands should be washed before a tampon is inserted into the vagina.
Tampons should be changed every three to four hours: it is important not to leave a tampon in for too long (never more than 8 hours). There is a condition called Toxic Shock Syndrome which can happen when bacteria (germs) multiply very fast in the vagina releasing a toxin (poison) which can cause women to become sick with symptoms such as feeling unwell, fever, rash, diarrhoea and headache.
There is no medical reason why women can’t have sex during their period. Some women prefer not to because of personal, cultural or religious preferences. It is important to practice safe sex at any time to prevent contracting sexually transmissible infections such as Chlamydia, HIV or Hepatitis B.
It is possible to become pregnant during a period. Even though ovulation usually happens from day 7-10 of the menstrual cycle (about 2 weeks before a period), it is possible for a woman to be fertile late in her cycle, up until the day the period begins or early in her cycle while she still has her period. It is also possible for sperm to stay alive inside the woman’s tubes for up to a week. So if a woman does not want to become pregnant, it is important that she uses a reliable form of contraception.
A period can be different from woman to woman, some women have very heavy periods others have a very light flow and both can be quite normal.
Sometimes though, bleeding is not normal and may be too heavy and cause a woman to feel very tired or dizzy or cause the iron levels in the blood to get too low.
It is important for a woman to see a doctor about the menstrual cycle if she is/has:
A woman should also see a doctor if