MUST READ.....SEE REASON WHY MENSTRUAL BLOOD DOES NOT CLOT

hehehehe.....The answer to your question of "what's the reason behind  menstrual blood 
not clotting" is put very simply. Normal menstrual blood does clot, 
menstrual blood contains not only blood but also tissue from the lining of 
the uterus.

 The hormones estrogen and progesterone  make the eggs in the ovaries 
"mature" and prepares the uterus for pregnancy. Once a month, one egg 
matures and leaves one of the ovaries, heading down one of the fallopian 
tubes toward the uterus. During this time, while the egg is traveling, the 
uterus begins to build up its lining with extra blood and tissue, making 
the walls of the uterus thick and cushioned. If the egg reaches the uterus 
and is 
fertilized by sperm, it attaches to the cushiony wall of the uterus, where 
it uses the extra blood and tissue to nourish and protect itself as it 
slowly develops into a baby. 
In most cases, though, the egg isn't fertilized by sperm, and is just 
passing through instead. When this happens, the egg dissolves and the 
uterus, no longer needing the cushioning for the egg, sheds the extra 
tissue lining. The blood and tissue leave the uterus, going through the 
vagina on its way out of the body. This is a menstrual period. This cycle 
(an egg being  released once a month and the uterus building itself up and 
then shedding its lining when it's 
not needed) will happen almost every month for several more decades - until 
a woman no longer releases eggs from her ovaries

Passing of blood clots during periods is a phenomenon which every woman experiences at one or other time of her reproductive years. While they may ring a warning bell in your ears, the fact is that most of the time passing clots with menstruation blood is absolutely normal even when the clots are quite big in size.

Even when passing of clots is normal it is important to know when they can indicate a possible underlying problem.

Normally blood produces anticoagulant factors which maintains the viscosity of blood and do not let blood clot but sometimes when the flow is heavy these anticoagulant factors do not get enough time to work and hence clots begin to form. However, this is a normal phenomenon during periods.
Somehow blood clots become a cause of concern when they are larger than the size of a woman’s fist, passed throughout the periods excessively, occur after periods and come along with pain.

The Common Causes Of Blood Clots Include

Poly Cystic Ovary Syndrome (PCOS)

PCOS is the most common female hormonal problem. When a woman suffers from PCOS the delicate balance between the female hormones – estrogen and progesterone gets disturbed. This disturbance leads to irregular and heavy bleeding along with passage of clots.

Endometriosis

When the inner lining of the uterus, which is known as endometrium, begins to grow outside the inner part of uterus, it is known as endometriosis.
This mucous membrane behaves just like normal endometrium mucous membrane and begins to bleed during the periods. This lining comes out in globs which look like big clots coming out during periods. Endometriosis is a painful condition too.

Uterine Fibroids

Uterine fibroids are a common occurrence during childbearing years. According to an estimate, 1 in 5 women have uterine fibroids. The good news is that uterine fibroids are benign (non-cancerous) tumors. They grow either inside the uterine cavity or on the uterine wall.

Fibroids can be very tiny which needs to be seen under a microscope but they keep on growing slowly till the woman menstruates and they can become quite big in size over a period of time. Generally, more than one fibroid grow in a woman’s womb. These fibroids are hypersensitive to the hormone estrogen. During periods, when a woman’s estrogen levels grow, these fibroids also grow and their growth causes heavy bleeding along with large blood clots.

Polyps

Polyps are fibroid like foreign growths in the inner wall of the uterus which tend to bulge out in the uterine cavity. If these polyps grow big in size then they tend to obstruct the flow of blood from the uterus during menstruation periods. This accelerates the process of clot formation in the uterus.

Other Chronic Factors

Some other chronic factors in body which tend to affect the balance between the two female hormones can also lead to blood clots during periods.
These factors include sudden weight gain or weight loss, long term use of steroids, changes in hormonal levels of a woman due to menopause, use of hormone based medications for infertility or other reproductive problems, etc.

Enlarged Uterus

During pregnancy the uterus size grows in order to accommodate the growing baby. Post delivery, the uterus begins to shrink to come back to its normal shape and size. Sometimes, when the uterus does not shrink back to its normal size it causes a large amount of blood pool into uterus. This blood tends to clot inside uterus before being passed out and results in big clots during menstruation.
If the passage of large blood clots becomes a regular feature along with painful cramps then it should be taken seriously and medical advice should be sought to rule out any abnormality.