There are, however, some ideas as to why one might miscarry and they are:
1) This may be due to the quality of an egg (source: http://www.isletsofhope.com/diabetes/print/polycystic_ovarian_syndrome_pcos_1.html)
2) Low progesterone levels. Progesterone is one of the important hormones during the first trimester of pregnancy that cause and "hold" the implantation of the fetus. Women with PCOS that become pregnant should have their progesterone levels monitored. (source: http://www.isletsofhope.com/diabetes/print/polycystic_ovarian_syndrome_pcos_1.html)
3) Excess Androgen levels (source: http://www.medscape.com/viewarticle/573733_1) Many studies alsosuggest that women on Glucophage (metformin) who become pregnant have a lower incidence of miscarriage if they stay on the drug at least during the first trimester of pregnancy. The safety of Glucophage during pregnancy and nursing has not been fully evaluated.
Putting two and two together... While most PCOS women are prescribed metformin in effort to encourage ovulation in effort to get pregnant, it should be noted that ovulation most likely returns because certain levels in the body are returned to "normal", including androgen levels that were in excess. According to a study outcome conducted in May of 2008, "An elevated Free Androgen Index (FAI) appears to be a prognostic factor for a subsequent miscarriage in women with recurrent miscarriages (RM) and is a more significant predictor of subsequent miscarriage than an advanced maternal age (≥40 years) or a
high number (≥6) of previous miscarriages (in this study)." (source: http://www.medscape.com/viewarticle/573733_1)
So far, that is the bulk of my findings. I'm not sure if it tells us a whole lot, except for it seems that every woman with PCOS should seriously consider being on metformin while TTC and, perhaps, continuing it through the pregnancy to some degree. It also seems that each woman should have their progesterone levels tested when they are TTC and may need to be put on progesterone during the last part of a cycle (http://pregnancy.lovetoknow.com/wiki/Prometrium_to_Prevent_Miscarriage). Continuous monitoring after getting pregnant to insure levels are at an acceptable level, and if not, should ask her doctor about staying on progesertone through at least the first part of pregnancy.
Obviously, I am not a doctor, so please take this info as purely an opinion. You should always consult your own doctor as to the best course of action for your personal health needs. These are just some of the things that I'm beginning to find as I collect information that might help me get pregnant and stay pregnant.
I will update this post, should I find any new information that might be useful. Please comment if you have additional details that would be helpful for those reading this blog. Education is power!