First and foremost, ask yourself the Following question.
Am I responsible enough to prevent my dog from producing an unintentional litter?
If your response is, "No," or "I'm not really sure," I strongly encourage you to have your dog sterilized. Preventing unintentional litters and pet overpopulation trump all other considerations. Check out the neutering/sterilization options described within this website.
If your reply is a very confident, "Yes," I encourage you to weigh in on the information presented within this website. Discuss what you learn here with your veterinarian and, together, determine if your dog should be neutered/sterilized. If so, at what age and via which procedure?