A menstrual cycle that has wide variations in the length of time between periods
Periods start at puberty and continue until the menopause. The average menstrual cycle lasts 28 days, but periods may occur as often as every 24 days or as infrequently as every 35 days or more. After puberty, most women develop a regular menstrual cycle with a relatively consistent length of time between periods. In some women, however, periods remain irregular. Menstrual bleeding normally lasts between 2 and 7 days, with the average length of bleeding being 5 days.
Variations in the length of the menstrual cycle are usually the result of a temporary hormonal imbalance. Fluctuations in hormone levels during puberty mean that periods are often irregular when they first start, and wide variations in a woman’s normal pattern of bleeding are common in the first few months following childbirth and with the approach of the menopause.
Hormonal imbalances at other times may be caused by factors such as stress, depression, and severe or long-term illness. Excessive exercise and extreme loss of weight (see Anorexia nervosa) or a marked increase in weight are also common causes of hormonal disturbance that can cause menstruation to become irregular.
Occasionally, irregular menstruation may be a symptom of a disorder of the ovaries or of the uterus. For example, polycystic ovary syndrome, in which there is an imbalance of the sex hormones, or endometriosis, in which fragments of the tissue that normally lines the uterus are found attached to other organs in the pelvis, may disrupt periods.
In some cases, an unsuspected pregnancy produces irregular bleeding that could easily be mistaken for a period. A single, late, heavy period may be due to a miscarriage. If you have a late period that is accompanied by severe abdominal pain, you should seek medical attention urgently because it may be due to an ectopic pregnancy. In some cases, the cause of irregular menstruation is unknown.
Irregular periods due to the normal hormonal changes that follow puberty or childbirth usually become more regular with time. In women who are approaching the menopause, irregular periods will eventually cease altogether. In all these cases, treatment is not usually necessary. However, if the problem persists and interferes significantly with a woman’s lifestyle, drugs, such as oral contraceptives, may sometimes be given to help regulate menstruation. Irregular menstruation that is due to extreme weight change, excessive exercise, stress, or depression should become more regular if these problems can be overcome.
If there is no obvious cause for your irregular periods and no apparent pattern to menstrual bleeding, your doctor may arrange for you to have tests to look for an underlying disorder. These may include a pregnancy test, blood tests to measure hormone levels, and ultrasound scanning of the pelvic region to look at the ovaries and uterus. If an underlying disorder is discovered, treatment of that disorder should regulate periods in most cases.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.