How often do potential employers check with previous employers?

Sorry if this question has been asked before.

Basically, I just got fired from a job and had a very successful interview with a new employer. The interview got me thinking that if the new employer calls my previous employer the new employer will reject me since I was only there for a few months and I was terminated on top of that.

How likely is it that they call my previous employer? Does the termination ruin all chances of getting the new position?

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official