A miscarriage can occur in many forms. A natural miscarriage occurs when the fetus or placenta is expelled through the woman's vagina. You can get more information by watching this video: Facts on Miscarriage.
How Do You Miscarry Naturally?
There can be a lot of reasons for a lady to miscarry,ie some women carry the fetus very low and any shock or trauma to the uterus will cause early delivery ie sex, a fall or knock of any sort riding in a car over rough terrain etc....a doctor can usually tell you what caused the miscarriage, the fetus may not be fully attached to the walls of your uterus, some females have had to be on complete bed rest during most of the term of pregnancy......the best to you