I don't believe in this too....when i got pregnant, we move house (country), everything was already settled so we cannot postponed the move anymore, i was 6 weeks pregnant, on the day the movers moved our bed/furniture out, i had bleeding, to make the story short, i lost the baby.
So, on my next pregnancy, i make sure, nobody will nail, move nor do anything with our bed....ahhahahah....supertitious or not, just follow it if you had bad experience before.
I now have a healthy gorgeous baby. Good luck!