Is it possible to tell if female dog is spaded/neutered or not?

there is this dog tht i have n she's not mine she came to my doorstep n she had a collar but no tags so i thought she would go back to her home but wen i came home from school SHE WAS STILL THERE so i let her in my house n she was house trained n im keepin her until i find the owner but anyways there is this boy dog tht comes into my yard n hes out there wen she's out there so is thtere any way to find out if she has been spaded or neutered so i will know if she might get pregnant cuz i know very well tht boy dog IS NOT neutered