Will getting too many pre-approal or pre-qualification affect my credit?

[Gordon Wong]

Will getting too many pre-approal or pre-qualification affect my credit?
I ask because they usually expire in 90 days and will need a new one after that.
Also, this property which is a short sale is requiring pre-approval through their lender even though I have one with another bank already.
So will it affect my credit if I keep getting pre-approal or pre-qualification?
Thank You