Some time ago I played a hand like that. I was South. This is the exact scenario I imagined on the first day I learnt bidding. I have asked a number of more experienced player and they usually told me not to worry too much about it. One told me if that happened the opponents probably had game. It seems he's correct. The result was down 5 for declarer (about +6 IMP for us) which essentially means it could have been 5C made for S/N.
I personally would not open with 4-3-3-3 12 HCP. What would your bidding as E/W be?