No.. if you are spotting or high risk pregnancy is something else..something is not right in your body.... not from transvaginal u/s....
I believe if you have rough intercourse while pregnant and penatrate deep.. then you might have spotting and the risk of miscarriage could be happen.. but never heard of transvaginal u/s.
I don't think it is very likely. A t/v ultrasound does not penetrate the cervix as far as I know so not sure how it could increase the chances of a miscarrriage. It can definately cause a bit of spotting, just as intercourse can as it can irritate the outside of the cervix a bit. Having a pap smear or internal exam during pregnancy can do the same thing. However, if there was any chance at all of it causing miscarriage I think its a safe bet that the procedure would not be used.