I keep hearing sperm can survive the same days through menstruation as without it, but in other places I see that sperm cannot last long cause of the hostile and acidic environment of the vagina? Can it survive 3-5 days of a period or will it die in hours to a day??
riddler, When she menstruates, sperm will have to fight it's way up the cervix and uterus against the outflow of the menstrual debris. Once it is in the fallopian tubes, the sperm will be fine.
They might however be weakened and much less than needed for fertilization. During her fertile period, she has fertile cervical mucus that will nourish nd protect the sperm. During menstruation there is no such a thing.
The ovulating ovary will also signal the sperm so that the vast majority will go to that side. During menstruation, that does not happen.