Will all miscarraiges pass naturally i have had many and no d&c for any will they pass on their own in all cases or what complications can happen?

Many, not all: Some women may retain part or all of the non-viable fetal part in their uterus after a miscarriage- called missed abortion. It can cause infection or bleeding. Another possibility is ectopic pregnancy, where the embryo is outside of the uterus, and can also cause massive internal bleeding.

No: This depends on the stage of the pregnancy at miscarriage. One can have retained products and bleed heavily. Very early pregnancies usually all pass without interventiion. It is very improtant to follow up with your pcp/gyn to make sure that you have completed the miscarriage and that your pregnancy hormone levels retun to normal. There can be complications.