Abnormal Menstrual Cycle (Length, Bleeding) Duration and Causes

Despite it being a normal physiologic process for young girls after puberty and for women before menopause, there is often confusion about what constitutes a normal menstrual cycle. Sometimes unusual patterns in the menstrual cycle may be deemed as abnormal variations. However, at other times an abnormal menstrual cycle are due to diseases that require medical treatment.

What is a normal menstrual cycle?

The menstrual cycle is the sequence of hormonal an physiologic changes that occur in preparation for pregnancy. This should occur in every female of reproductive age. It is a carefully coordinated sequence of fluctuation in female hormone levels. This causes changes in the anatomy and physiology of the female reproductive system. However, if pregnancy does not occur then the cycle is “reset” to recur again approximately every month.

Read more on menstrual cycle.

The menstrual cycle is marked by two major events – ovulation and menstruation. Ovulation occurs about midway through the cycle. The ovary releases an egg cell (ovum) which travels down the fallopian tube to the uterus (womb). If this ovum is not fertilized within days then the body prepares to remove it and “reset” the cycle. This is marked be menstruation where there is bleeding with the inner uterus lining (endometrium) and ovum expelled.

Length of Normal Menstrual Cycle

The average menstrual cycle lasts for 28 days. This is the duration from day one of the menstrual period (menstruation/menstrual bleeding) to day one of the next menstrual period. However, it is important to note that the average menstrual cycle length is not necessarily normal. It can be as short as 21 days and as long as 35 days and still be considered normal.

Duration of Menstrual Bleeding

The average duration of menses (period or menstrual bleeding) is 3 to 5 days. As is the case with the length of the menstrual cycle, there may be a shorter or long duration of menstrual bleeding. Therefore the average does not necessarily indicate what should be considered as normal. This means that a period can vary from 2 to 7 days and still be a normal duration for a period.

Read more on amenorrhea.

When is the menstrual cycle abnormal?

The menstrual cycle would be considered abnormal if it is shorter than 21 days or longer than 35 days. Furthermore if the duration of menstrual bleeding is for just for 1 day or does not occur (amenorrhea) then it would also indicate an abnormality with the menstrual cycle. Similarly menstrual bleeding for more than 7 days may also be a sign of an abnormal menstrual cycle. Another factor that is not always considered is the regularity of a menstrual cycle in that every cycle should last for approximately the same duration.

There are several reasons for these abnormalities in the menstrual cycle. Sometimes it may occur suddenly and only for one or two cycles with the normal menstrual cycle restoring thereafter. At other times it may be drug-induced or caused by some substance that is intentionally or accidentally consumed. Apart from pregnancy, perimenopause and menopause, other causes of abnormal menstrual cycle are some disease or disorder that may require medical intervention.

Causes of Abnormal Menstrual Cycle

The most common causes of an abnormal menstrual cycle have been discussed in detail below. It is important to note that sudden and short term changes in menstrual cycle can occur with the stress and the use of certain drugs. Stress refers to both physiologic stress as may occur with severe illness or trauma. It also refers to psychological stress, particularly acute stress as may occur with grief.

Pregnancy and Perimenopause

Pregnancy and perimenopause are two normal physiologic events whereby there is a disturbance in the menstrual cycle. In pregnancy there is a cessation of menstruation (no periods) for the duration of the pregnancy and for a short period after childbirth. It may also continue for longer periods if a mother breastfeeds.

Irregular menstruation is a normal part of perimenopause. This is the phase in a woman’s life as she transitions to menopause where menstruation ceases completely. During perimenopause the cycle and menstruation may become shorter or longer. Menstrual bleeding may also be lighter or heavier than normal.

Read more on abnormal vaginal bleeding.

Polycystic Ovarian Syndrome (PCOS)

Polycystic ovarian syndrome (PCOS) is a condition in women of reproductive age where there is a disturbance in the hormone levels. The menstruation is irregular, androgen (male sex hormone) levels are elevated and cysts may develop in the ovaries. There is also an associated disturbance in the insulin levels. PCOS is one of the leading causes of female infertility.

Uterine Fibroids

Uterine fibroids, also known as leiomyomas, are abnormal growths in the muscular layer of the uterus (myometrium). These growths are non-cancerous (benign) and are not associated with an increased risk of cancer. Uterine fibroids are common growths that arise in the uterine wall but most women never have symptoms. However, in symptomatic cases there may be heavy menstrual bleeding, longer than normal periods and pelvic pain.

Pelvic Inflammatory Disease

Pelvix inflammatory disease (PID) is inflammation of the female reproductive organs as a result of an infection. The infection is usually sexually transmitted and spreads from the vagina. It may involve the uterus, fallopian tubes and even the ovaries. Pelvic pain, foul-smelling discharge, difficulty urination with/without pain and abnormal vaginal bleeding are the main symptoms seen with PID.

Oral Contraceptives

Oral contraceptives (birth control pill) is used to prevent pregnancy. The alteration of the hormone levels with this medication usually results in a stable and apparently normal menstrual cycle. However, ovulation does not occur. The menstrual bleeding occurs when there is a sudden drop in the hormone levels. If the pill is not used as directed and taken regularly, then the menstrual bleeding may be irregular or sometimes even absent.

Eating Disorders and Dieting

Changes in nutrition can also upset the menstrual cycle and lead to irregular periods. Sometimes there may be no period. This disturbance is usually a result of inadequate food intake, as may occur with eating disorder like anorexia nervosa or with extreme dieting.

Excessive Exercise

Excessive physical activity may also cause a disruption of the menstrual cycle. This is more likely to be seen among professional athletes or sportspersons. However, it can occur in any woman who is exercising excessively. Typically there may be infrequent periods and sometimes even no periods.

Thyroid Disorders

Thyroid disorders in women can also impact on the menstrual cycle, leading to irregular or missed periods at one end or very frequent periods and excessive menstrual bleeding at the other. Ovulation may also not occur in some cycles. This abnormal menstrual cycle and very light or heavy menstrual bleed may be seen with both an underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism).