The Menstrual Cycle-Basic Facts


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The main defining feature of the Menstrual Cycle is the menstrual period - this is defined as the spontaneous, monthly, cyclical, bloody vaginal discharge that represents shedding of the endometrium (inner lining of the uterus) every month. Once shedding is complete, it stops spontaneously. The term 'menstruation' comes from the Greek word 'men' meaning month.

Different people call menstruation by different names. Some call it the 'period', some call it 'menses' while others call it the 'monthly'.

Menstruation occurs throughout the reproductive period of a woman's life from menarche (beginning of menstruation) to the menopause (ending of menstruation).

Each menstrual cycle starts on the first day of the menses and ends on the day before the beginning of the next menstrual period.

The normal length of a menstrual cycle is 28 days (4weeks). But it varies from woman to woman. It can be as early as 7 days before the date or 7 days after the date - in clinical terms, a normal menstrual cycle is written as 28 +/- 7 days. So a menstrual cycle length between 3 weeks to 5 weeks is considered normal.

But if the period does not occur within 5 weeks of the last period, then it is called a delayed menstruation or delayed period.

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The duration of a normal period is 4 -5 days. But it can be as less as 2 days or as long as 7 days.

Any period or menses, which lasts for less than 2 days or more than 7 days is considered abnormal and the cause of this abnormality needs to be investigated.

When the blood flow lasts for less than 2 days, it is called a scanty period or oligomenorrhoea .

A scanty blood flow also occurs at the time of the implantation of the ovum in early pregnancy. Known as implantation bleeding, this is often considered a scanty period and ignored, leading to a delayed diagnosis of pregnancy.

The total blood loss in an average menstrual period is about 35 - 40 ml (about 3 - 4 tablespoons). But a loss of upto 80 ml is considered normal. This results in a loss of about 0.6 to 0.7 mg of iron each month.

If bleeding occurs within 1 - 2 weeks after the last period, then it is likely to be due to midcycle bleeding or ovulation bleeding. This is more so if the bleeding is minimal or less than normal, brownish or pinkish, and clears up within 4 -5 days.

The menstrual cycle is initiated by hormones released by the pituitary gland in the brain.

These hormones - the Follicle Stimulating Hormones (FSH), and the Leutinising Hormone (LH) - stimulate the ovaries to go through the ovarian cycle and produce estrogen and progesterone.

Estrogen and progesterone, in turn, stimulate changes in the uterus, known as the uterine cycle. Menstruation is one of the phases of the uterine cycle.

The changes in both the ovaries and the uterus can be easily diagnosed by non-invasive methods like ultrasonogram (USG) and blood tests for the levels of the various hormones released by the ovaries and the pituitary.

Invasive methods like dilatation and curettage (D & C) of the uterus can also be used for a diagnosis .

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