To explain why it is impossible to get pregnant during time of menstruation, from a theoretical point of view quite easily. Ideally, ovulation — the most favourable period for the occurrence of pregnancy occurs in women in the middle of the menstrual cycle, i.e. approximately 2 weeks after the beginning of the previous month and 2 weeks before the subsequent menstruation. Male sperm generally retain their activity for only one week after entering the woman's vagina. It turns out that to get pregnant at the time of menstruation impossible.But as you know, every rule has its exceptions. And in fact, the probability of pregnancy at the time of menstruation exists. The chances of getting pregnant at the time of the monthly increase in women living irregular sexual life, which leads to disruption of physiological processes of the reproductive system. The cause of the pregnancy at time of menstruation can also be something as rare as the maturation of two eggs. Irregular menstrual cycle and its abrupt change usually lead to shift the timing of ovulation. But it can also lead to the pregnancy in time monthly.Remember that getting pregnant can not any day of menstruation. The first few days of menstruation accompanied by profuse discharge, which have a very negative impact on the livelihoods of entering the woman's vagina, sperm and even kill male sex cells. Consequently, the probability of getting pregnant there are only a few days before menstruation, which should come out unfertilized egg. Thus, it appears that becoming pregnant during the time of menstruation, but rather in their last days, it is still possible.