Hi again. I think it would help with getting you a more direct answer which applies to your situation if you gave a few more details and the situation as well. If you don't know already, you can click the 'leave a comment' at the bottom of an answer inside the box with the answer and a box will come up to do that with. You can also include further details in your questions if you run out of room by clicking the 'add further details' link and the box will come up in a minute (a little longer sometimes but it does come up).
Is it that you are concerned about a female accidentally getting pregnant and whether you should worry or take precautions or is it something like wanting to breed a dog with retained testicle(s) or wondering id it's possible he could get a female pregnant or something else? What breed? How old? Where did you get him? Is he neutered? If so was it very recently? Is it that he has one or both testicles retained instead of being neutered? Are you unsure of his history and maybe whether his testicles are retained or he is neutered?
If he has been neutered and has no testicles he most likely can not get a female pregnant though occasionally there is a short period of time just after the neuter where it is possible from any storage. Neutering stops the production.
If he has one testicle retained it is still possible though there is less production and if both retained the chances are even lower (pretty low) but also still possible. A dog should not be bred if one or both testicles are retained.
If he is a young puppy under three months of age it's not really a concern, three months is unlikely but has happened on occasion, 4 months it's more likely but still not too many 4 month old sires running around but still pays to be careful, 5 months and beyond, keep them completely separated at all times with NO way to get to her at least 7 to 10 days after she has stopped bleeding and monitor carefully for signs she may still be receptive before allowing them around each other.
Lastly, females don't breed at will. They must go into season (commonly referred to as 'heat') first.
Did any of that help at all? :-)www.irvinevetservices.com www.irvinevetservices.com www.learntobreed.com www.dogfoodanalysis.com