Your chances of conceiving are the highest when you have sexual intercourse before and during ovulation but you can still fall pregnant during your period. This is because sperm can survive in the uterus for up to 5 days. Hence, if you have sex near the end of your period, there is a possibility that the sperm can fertilise an egg after it is released during ovulation. Overall, this is a rare occurrence and it is more likely to occur for ladies who have a shorter menstruation cycle.