the time when a girl is most likely to become pregnant — can happen within a few days of when your period ends. Also, sperm can fertilize an egg for 72 hours (3. Does having your period after having had sex mean that you are safe from is whether you can get pregnant if you have had sex immediately. When Riley didn't get pregnant right away, she worried about infertility. But before seeing a An egg can live up to 24 hours after ovulation. Continue Reading Phone apps can help you chart your cycle. You record details.