It takes awhile for the heat cycle of a female dog to become regular. An owner can determine if the dog is in heat by the dog's behavior and by the appearance of the vulva, which will become swollen during her cycle.
A dog in heat may urinate more frequently and may become more restless. A blood-stained discharge from the vulva is common, and the female will often become more receptive to the attention of male dogs.
Due to the increased blood flow during a heat cycle, spaying during this time is not recommended. Many vets prefer to spay a female 4 to 6 weeks after the end of the heat cycle.Learn more about Dogs