A female dog comes into heat and is able to get pregnant every six to eight months.  Her first heat takes place when she is about six months old and lasts for roughly three weeks. She is generally most fertile around the tenth day. Aside from a small bit of vaginal bleeding and increased urination, the most noticeable symptom of heat may be the attention that male dogs pay your pet. To determine if a female dog is in heat and when she is most fertile, a breeder will generally test the dogs progesterone levels. This hormone peaks when the dog has ovulated. This way it can help a dog owner know when to breed the dog.  So don’t do anything differently with your pet, continue to exercise her and take her for long walks on her dog leash but watch out for all she may get from the male dogs!