Dear Caroline,
I'm so sorry for your loss and for not posting earlier. I've been away in Australia for a scientific conference.
As a mother who lost 8 pregnancies to recurrent miscarriage before my sons were born I undersstand how devastated you must feel.
Routine blood tests don't really tell us very much. One you have had 3 losses most recurrent miscarriage specialists would recommend a complete work-up to rule out an immune issue. But this should be handled by a specialist in the field. Recently I attended a post graduate course on this topic given by the American Society of Reproductive Medicine. One of the doctors who spoke was Dr. William Kutteh who is a reproductive endocrinologist specializing in recurrent miscarriage. You may want to arrange a visit with him or at least a telephone consult:
http://www.fertilitymemphis.com/medicalteam.aspBest, Lenore