I am assuming that if your levels where in Labs range, miscarriage should not be due to hypothyroidism. Normally miscarriage is connected to hypothyroid when TSH level is greater than 6 or 8. Although I am not a doctor, so you might want to address your question to:
Mark Lupo, M.D. at "The Thyroid Disorder Forum" Medhelp at
http://www.medhelp.org/forums/thyroid/wwwboard.html
It might take a few days for the doctor to answer, so be patient and keep checking in.
Good Luck!
GL
Hyper/Graves'/RAI