Untreated miscarriage does not cause ovarian cysts. Neither does ovarian cyst cause miscarriage.To accept that someone had miscarriage, there should be some evidence of one being pregnant i.e. either blood / urine test, ultrasound scan or histology of the tissue which was expelled out of uterus (aborted tissue). From your history it is not clear on what basis you are assuming you had miscarriage. I am therefore not convinced that you had miscarriage. If you are saying that you miscarried on the basis of missed periods, you might well had delayed periods - which is not uncommon.Not all cysts on ovaries indicate pathology (disease). It is very common to see physiological / functional cysts on the ovary depending on which phase of your cycle you have the scan. Therefore your doctor should explain the cyst in further details as to what it looks like and what needs done. Mere presence of cyst on the ovary does not mean much. Further information is therefore needed regarding the size, appearance and other features of the cyst to make any comment on it's implications.