Join Date: Nov 2010
Location: Northern Illinois
Was he gelded when you got him?
How long have you had your mare? Is it possible she was bred before you got her?
If the answer to the above is both yes, he was always gelded, and no, it is not possible she was bred, then it is impossible for her to be pregnant.
If you have serious doubts, call a vet.
But I would make sure to figure it out. Either one needs to be addressed. If she is that overweight that you think she may be pregnant, she needs to go on a diet as her risk for founder or colic goes way up. Or the alternate is that she is pregnant and needs to be taken care of (mare care and careful monitoring).
** Don't be the rider who gallops all night and never sees the horse that is beneath him **