Each pregnancy behaves separately. Also some causes
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.