It is the natural cycle every woman experiences every month. Some women have PMS and some don't. If you ask others, they would usually say that having menstruation every month means you have become a real woman.

However, nobody really knows the reason why women menstruate. According to an article in Live Science, it still remains a big mystery why women have this cycle every month. Many researchers might have figured out at some point why this happens, but there are still a lot of things that are not known. They said that there should be a better understanding of the hows and whys of menstruation. This is because for a week of every month 20 to 30 percent of women are unable to have a normal life because of menstrual problems.

Dr. Hilary Critchley, an ob-gyn and reproductive health researcher at the University of Edinburgh in Scotland said, "There's so much we don't understand about why this repeated event of shedding and repair happens. It's so crucial for the reproduction of our species. But it's not a popular topic to study. There's a big to-do around talking about problems that people don't see."

On a study that will be published in an upcoming issue of the journal Human Reproduction Update, she said that over the last 40 years menstruation is defined as the loss of the endometrium, or the tissue that lines the inside of the uterus. However, there are still a lot of things that are unknown and how it really affects women's health. Some women have heavy flows or bleeding during the period, this can be because of uterine fibroids or endometriosis. However, there are still some women who had heavy bleeding because of other reasons.

Researchers aren't sure whether the cause of heavy bleeding lies in the lining of the uterus itself or in the mechanisms that normally control the bleeding. Moreover, researchers don't know whether the cause of heavy bleeding is the same in women with fibroids as in those with endometriosis, or in women without either condition.

Finally, women who have suffered heavy bleeding for many years just opt to have surgery to remove the unterus, even if some of them are young and haven't had any children yet. Critchley said that women can't do anything about these problems. They actually don't want to have surgery, but if they seek for other treatments, it may not work or might have side effects. She added that there is no other choice for medical treatments that can be offered to cure this condition.