Brief answer: 3 days before and 2-3 days after the ovulation (which occurs on 14th-15th day of menstrual cycle) Detailed answer: Sperms can live in a woman’s body up to 5 days after intercourse, though more often 2 days. Pregnancy is most likely if intercourse occurs anywhere from 3 days before ovulation until 2-3 days after ovulation. Since the exact time of ovulation cannot be predicted, we add 2 to 3 days to the beginning and end. Day 1 in the Menstrual Cycle is the first day of bleeding. Your menstrual periods must be regular for at least six months and ranging from 26-32 days to use this fertile days calculation System. Frequency of coitus depends upon the sexual partners but repeated coitus may result in exhaustion, dry ejaculate, dehydration and some times bleeding.