They will question thee concerning
the monthly course. Say "It is hurt;
so go apart from women during
the monthly course, and do not approach them
till they are clean. When they have cleansed
themselves, then come into them as God
has commended you". Truly, God loves
those who repent, and he loves those
who cleanse themselves.
Chapter 2 verse 222
Practicing sexual intercourse during menstruation is forbidden because the womb at that period is inflamed and easily exposed to bacteria. Dr. El Bar says that blood is the best environment for microbes to increase and flourish. Besides, the capacity of the womb to resist the invading microbes, that exist on the penis, decreases that constitute a great danger for the womb. The resistance of the vagina becomes also very low, because the acid which it throws out and which kills the microbes decreases during menstruation.
That is why, goes on Dr. El bar sexual intercourse during menstruation is but letting microbes in, at a time when the womb could not resist.
It is not only women who are hurt, but men are also hurt. The increase of microbes leads to inflaming men’s urinary tracts. The microbes could also invade the prostate, then to the spermatic cord and the spermatocyst, which could block the sperm duct and hence causes impotency.
It is not only that but other diseases also attack both women and men so the Holy Qur’an forbids such unhealthy practice and in this it is also ahead of science and scientists.