Can anyone explain me why do they recommend to stay in bed with your legs up (in case of threatened m/c & some bleeding)? does it really work? I have several months ahead of me waiting to TTCAL again. I want to be prepared this time

. On the day before I had a m/c I spent several hours digging a hole in my back yard... now I am wondering if that could have cause my second m/c...
also, have you heard anything about working out to have great stomach muscles before getting pg? I just don't know how that could help prevent a m/c..