Menstruation Explained: Why Do Women Have Periods?

Women have periods every month, starting from puberty up until menopause. But why is this the case?

Why Do Women Have Periods?

Menstruation, or a period, refers to normal vaginal bleeding that takes place as part of a woman's healthy monthly cycle. It typically starts during puberty, at the age of 11 to 14 years, and goes on until menopause, which is roughly around 51 years.

Each month, a woman's body prepares itself for pregnancy. The uterus lining gets thick, and an egg grows and gets released by one ovary.

If pregnancy does not take place, levels of progesterone and estrogen plummet. This eventually hits a level that tells the body to start menstruating. In the course of the period, the uterus sheds its own lining. It is then passed with blood out of the body via the vagina.

On average, a woman loses around two to three tablespoons of blood during menstruation.

The interval between periods typically lasts for around 28 days. Bleeding usually goes on for roughly four to five days. However, it is still possible for people to experience longer intervals between periods and have shorter periods.

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Menstrual Cycle Explained

Periods come as part of an overall process known as the menstrual cycle, which describes the events that take place in the body as it prepares for pregnancy every month. The menstrual cycle covers the first day of the period and lasts until the first day of the next period. While there are slight differences in each person's menstrual cycle, the process remains the same.

On average, the menstrual cycle takes place for 28 days. However, it may range from 21 to 35 days and still be considered normal or regular.

This menstrual cycle comes in four phases, namely, the menses phase, follicular phase, ovulation phase, and luteal phase. The process is generally triggered by hormonal rises and falls.

The menses phase starts at the first day of the period. This phase is marked by the shedding of the uterine lining if pregnancy does not take place.

On the other hand, the follicular phase starts on the day the period starts and ends during ovulation. It happens simultaneously with the menses phase, but ends when a woman ovulates. By then, estrogen levels go up, leading to the growth and thickening of the uterine lining. Moreover, a hormone known as FSH (follicle-stimulating hormone) makes the follicles within the ovaries grow. In the 10th to 14th days, one of the follicles will form an ovum, or a fully mature egg.

Ovulation takes place around the 14th day of the 28-day cycle. A sudden rise in LH (luteinizing hormones) makes the ovary release an egg.

The last phase, the luteal phase, goes on from days 15 to 28. The egg leaves the ovary and starts traveling to the uterus through the fallopian tubes. Progesterone hormone levels rise to help prepare the lining of the uterus for pregnancy. If an egg ends up being fertilized by sperm and links itself to the wall of the uterus, this would result in pregnancy. However, if pregnancy does not take place, levels of progesterone and estrogen go down, and the uterus' thick lining sheds again during menstruation.