Well, usually C-section is not the cause of miscarriage unless there is infection. Each pregnancy behaves separately. Also some causes of miscarriage are related to that pregnancy alone. Some causes tend to recur and you must be careful about these. Generally first trimester abortions or abortions occurring in first three months are due to fetal abnormality, genetic causes, Rh blood group incompatibility and low progesterone hormone. Infection of the uterus, endometriosis, fibroids, etc are some other causes for early abortion. You need to consult your gynecologist and run some tests to rule out these causes. Eliminating these causes will increase the chances of full term pregnancy. Take care!