While normal menstruation can last for only three days, according to the Cleveland Health Clinic, it is still possible to be pregnant while experiencing vaginal bleeding. The American Pregnancy Association maintains that vaginal bleeding is common during the first trimester of pregnancy.
Up to 30 percent of women experience vaginal bleeding in the first trimester, according to the American Pregnancy Association. Although it's a normal symptom for these women, vaginal bleeding during pregnancy is also sometimes a sign of a miscarriage, particularly during the second or third trimester. The Cleveland Health Clinic advises women who experience a period that stops suddenly to visit a medical professional.