low dose aspirin and Heparin injections

Hi,

I would like to have input from members who were given aspirin and heparin to avoid miscarriage. I know these are blood thinners and are given to avoid blood clot.

I talked to a doctor regarding my history of miscarriage, and she said I might have to go for aspirin and heparin shots for next preganncy though none of blood reports show I have thrombosis.

Is it OK to take heparin shots even if I may not be right candidate for it. Does it have any side effects. How long are these normally taken.

Sarayu