Menstruation, also known as a period or monthly, is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. Up to 80% of women report having some symptoms prior to menstruation. Common symptoms include acne, tender breasts, bloating, feeling tired, irritability, and mood changes. These symptoms interfere with normal life, and therefore qualify as premenstrual syndrome, in 20 to 30% of women. In 3 to 8%, symptoms are severe.
The first period usually begins between twelve and fifteen years of age, a point in time known as menarche. However, periods may occasionally start as young as eight years old and still be considered normal. The average age of the first period is generally later in the developing world and earlier in developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women and 21 to 31 days in adults (an average of 28 days). Menstruation stops occurring after menopause which usually occurs between 45 and 55 years of age. Bleeding usually lasts around 2 to 7 days.
The menstrual cycle occurs due to the rise and fall of hormones. This cycle results in the thickening of the lining of the uterus and production of an egg which is required for pregnancy. The egg is released around day fourteen in the cycle and the thickened lining of the uterus is to provide nutrients for a potential developing baby. If pregnancy does not occur, the lining is released in what is known as menstruation.
A number of problems with menstruation may occur. A lack of periods, known as amenorrhea, is when periods do not occur by age 15 or have not occurred in 90 days. Periods also stop during pregnancy and typically do not resume during the initial months of breastfeeding. Other problems include painful periods and abnormal bleeding such as bleeding between periods or heavy bleeding.Menstruation in other animals occurs in primates, such as apes and monkeys, as well as bats and the elephant shrew.
A period is the part of the menstrual cycle when a woman bleeds from her vagina for a few days. In most women this happens every 28 days or so.
It's common for women to have a cycle slightly shorter or longer than this (from 24 to 35 days).
Girls have their first period during puberty. Most girls begin puberty between the ages of 8 and 14, with 11 being the average age. The first period is called the menarche.
A woman's periods continue until the menopause, which usually occurs when a woman reaches her late 40s to mid-50s (the average age is 51).
The menstrual cycle
Each menstrual cycle starts on the first day of your period (day one) and lasts until the day before your next period begins.
The reproductive organs inside a woman's body consist of:
two ovaries – where eggs are stored, developed and released
the womb (uterus) – where a fertilized egg implants and a pregnancy develops
fallopian tubes – the two narrow tubes that connect the ovaries to the womb
the cervix – the lower part of the womb that connects to the vagina
the vagina – a muscular tube leading from the cervix to outside the body
During each menstrual cycle levels of the hormone estrogen rise as an egg develops and is released by the ovary (ovulation). Your womb lining thickens in preparation for a possible pregnancy.
The egg travels down the fallopian tube and if it meets a sperm and is fertilized, a pregnancy can occur.
The egg lives for about 24 hours. If it isn't fertilized, it will be absorbed into your body. The lining of your womb will come away and leave your body through the vagina mixed with blood. This is a period, also sometimes referred to as the menstrual flow or menses.
Symptoms associated with periods
During your period you'll bleed from your vagina for a few days. The bleeding will usually be the heaviest in the first two days.
Your period can last between three and eight days, but will usually last for about five days.
The amount of blood you lose during your period depends on how heavy they are. It's usually about 30 to 72 milliliters (5 to 12 teaspoons), although some women bleed more heavily than this.
When the period is at its heaviest, the blood tends to be red. On lighter days, it may be pink, brown or black.
If you have heavy periods, there are a number of treatment options available. If your bleeding isn't too severe, you could try using a sanitary towel or tampon with a higher absorbency.
There are also a number of medications to help reduce bleeding. For example, the levonorgestrel-releasing intrauterine system (LNG-IUS) is a small plastic device that's inserted into your womb and releases a hormone called progesterone. It prevents the womb lining growing so quickly.
Alternatively, tranexamic acid tablets work by helping the blood in your womb clot.
Changes in your periods
Your periods can change – for example, they may last longer or get lighter. This doesn't necessarily mean there's a problem, but it does need to be investigated. You can go to see your GP, or you can visit your nearest women's clinic or contraceptive clinic.
Bleeding between periods, bleeding after having sex or bleeding after the menopause needs to be checked by a doctor. It might be caused by infection, abnormalities in the cervix (the neck of the womb) or, in rare cases, it could be cancer.
If you miss a period and you've had sex, you could be pregnant. See your GP if you're not pregnant and you've missed two or three periods. Find out about taking a pregnancy test.