menstruation is the periodic shedding of the endometrium (lining of the uterus) accompanied by blood loss, that identifies the reproductive years of a woman's life. The first menstruation (menarche) usually occurs at puberty (typically between the ages of 11 and 16) and menstrual periods continue until the menopause around the age of 45–50. However, menstruation does not occur during
pregnancy and can be suppressed or disrupted in women who are breast-feeding. This was noted by the scientist and philosopher, Aristotle (384–22 bc), who believed that pregnant women did not menstruate because the seed of the male caused blood to coagulate into an egg from which the fetus developed. Milk was also thought to be formed from menstrual blood because of the absence of menstruation in lactating women.
The old ideas as to why women menstruate stemmed from the teachings of Hippocrates (
c.400 bc) who believed that health was governed by the balance of the four body fluids or
humours — blood, phlegm, black bile, and yellow bile. Thus menstruation was seen as a means of getting rid of excess blood to prevent the body filling with this humour, upsetting the balance and causing illness. This theory was finally disproved by John Davidge in 1814, who pointed out that a woman might only lose a few teaspoons of blood in a typical menstrual flow, while the loss of a much greater amount of blood through blood-letting (cutting the veins) did not prevent menstruation. He concluded that menstruation, rather than being a means of getting rid of excess blood, could be attributed to some odd condition of the ovaries which excited the blood vessels of the womb. In essence his premise was correct.
Menstruation is the culmination of a complex series of hormonal events associated with the cyclical production of a mature egg within the ovary and the release of this egg for fertilization. In the first half of the menstrual cycle, ovarian follicles, containing an egg, develop, and produce increasing amounts of
oestrogen. This sex hormone stimulates a build-up of the lining of the womb and the growth of spiral arteries into this thickened lining. After ovulation, which occurs around day 14 of the cycle, the empty follicle in the ovary becomes a corpus luteum. This produces high concentrations of
progesterone and some oestrogen. The progesterone further increases the thickness of the uterine lining and causes it to secrete a fluid which will nourish a fertilized egg and encourage implantation of the embryo. If fertilization does not occur the corpus luteum breaks down towards the end of the cycle and so the endometrium loses its hormonal support from the ovary. As a consequence the endometrium literally dies, and the cells of this lining are shed along with some loss of blood from the spiral arteries which have grown into the lining of the womb. Menstrual bleeding usually lasts 3–7 days, although endometrial regeneration can begin as early as the third day after the beginning of menstruation. Interestingly, only in man, apes, and Old World monkeys is the endometrium shed. In most other mammals the endometrium is resorbed at the end of each cycle and there is no bleeding — this is probably related to the absence of spiral arteries.
While the shedding of the uterine lining actually signifies the end of each reproductive cycle, the first day of menstruation is defined for convenience and accuracy as the beginning of a new menstrual cycle. Typically each cycle lasts between 25 and 34 days in 95% of women, with 28 days being the average. Hence the term ‘menstruation’, since it tends to recur at monthly intervals. Total blood loss during each menstruation varies from cycle to cycle, and in different women at different stages of their reproductive life. However, the average blood loss is about 50–60 ml (a teaspoon holds about 5 ml), although it can vary from about 10–80 ml. Excessive loss of blood (menorrhagia) can lead to iron-deficiency
anaemia.
Many myths, legends, and
taboos have grown up around menstruation throughout the centuries, but all with the underlying sentiment that menstruating women are unclean and capable of producing bad effects on the world about them. It became a focus of religious observance. For example, Hindu women are not supposed to prepare their husbands' food when they are menstruating. Those Moslem women who are normally allowed to pray in a Mosque may not do so during menstruation. Some Buddhists think it is wrong to enter a temple during menstruation and Jews are supposed to refrain from sexual intercourse during this time. In medieval times menstruating women were excluded from going to church and the Church of England has a service for ‘The Churching of Women’, a ceremony to be performed when a woman has had her first menstruation after the birth of a child. And so from the early teaching of Hippocrates, right through the centuries menstruation has been seen as a way of getting rid of something undesirable, unclean and potentially harmful. No wonder such derogatory terms as ‘the
curse’ came into existence.
Saffron Whitehead
