The 7 Signs That Your Dog Is Pregnant

two dogs playing and running

Bloody discharge, receptivity to male dogs, frantic behavior, and other indicators of a dog in heat can be seen. In each of the four phases of a heat cycle, an unspayed female dog will exhibit various symptoms. Although a bloody discharge is the most prominent symptom that your dog is in heat, it isn't the sole indicator that your pet is ready to mate. It might be difficult to live with an unspayed dog, especially if you already have an intact male dog, but understanding what to anticipate can help you avoid difficulties.

When Should I Expect My Dog's First Heat?

The age at which a dog goes into heat differs substantially across breeds. Toy breeds can go into heat for the first time as early as four months, but huge and gigantic breeds can take up to two years to go into heat. Most canines experience their first heat cycle between the ages of six and fifteen months.

What Signs Indicate That My Dog Is in Heat?

The more you understand your dog's cycle, the more prepared you'll be for any physical or behavioral changes that may occur during her heat cycle. You will observe various changes during each phase of her heat cycle, which may include the following seven signs:

  • Swollen vulva
  • Bloody or straw-colored discharge from the vulva
  • Receptive to male dogs
  • Excessive licking of the genital area
  • Agitated, nervous, or aggressive behavior
  • Urinating more frequently
  • Change in tail position

With clues gleaned from your female dog’s physical appearance and behavior, you can determine which stage of her heat cycle she is experiencing.

What are the Four Stages of the Canine Heat Cycle?

Your dog will go through four phases throughout her heat cycle, each marked by physical and behavioral changes. The following are the four phases of the canine heat cycle:

  1. Proestrus: Proestrus is the start of the heat period where your dog’s body is preparing to mate. Signs seen during this phase include a swollen vulva, blood-tinged discharge, excessive licking of the genital area, clingy behavior, and aggression toward male dogs. Your dog may also hold her tail close to her body.
  2. Estrus: The estrus phase is the mating phase where your female dog will be receptive to males. You may notice that your dog seems to be urinating more frequently than normal, as she is marking spots to indicate her readiness to breed. Although she may be leaving urine marks in areas, her vaginal discharge will slow and may change to a straw color. Since your dog is ready to mate, she will approach males with her tail held to the side but may be aggressive towards other females.
  3. Diestrus: This phase occurs directly after the “in heat” stage and allows your dog’s body to either return to normal or develop into a pregnancy. Her vulva will return to normal size and vaginal discharge will disappear.
  4. Anestrus: Anestrus is an inactive phase, and no signs of hormonal or sexual behavior are noticed.

How Often Will My Dog Go into Heat?

Dogs have two heat cycles every year, each around six months apart. Females with irregular cycles are more likely to be extremely young or very elderly. Small breeds may cycle three times each year, whereas big breeds may only cycle once a year. Canine estrous cycles are not affected by the seasons, sunshine, or temperature, as they are in certain other animals.

What Should I Do if My Dog Is in Heat?

If your dog is experiencing her first heat cycle, it can be an unsettling situation for both of you. Follow these tips to ensure her heat goes as smoothly as possible:

  • Never let your dog out in the yard alone. Do not underestimate a male dog’s drive to find a female who is emitting breeding pheromones. You may walk outside to find a strange male dog tied to your female.
  • Never let your dog off her leash when she’s in heat. Although your dog may have excellent obedience skills, her recall ability may fall by the wayside when she’s influenced by her hormones and is intent on finding a male.
  • Ensure your dog’s ID tags and microchip information are up-to-date. If the unthinkable happens and your dog escapes from your yard or runs off, ensure you can be reunited with legible, updated ID tags and current microchip contact info.
  • Consult your veterinarian if you notice signs of illness. Occasionally, a female dog can experience health issues after a heat cycle when the uterine lining remains thickened and produces more fluid, creating the ideal environment for bacterial growth. This can lead to a life-threatening pyometra, or uterine infection. A pet with a pyometra may drink or urinate excessively, produce thick vaginal discharge, or have a decreased appetite, abdominal pain, vomiting, or lethargy.
  • Consider spaying your dog after her heat cycle is over. If you have no plans to breed your dog, consider waiting until after her heat cycle is over to spay her. Your veterinarian can advise you on the appropriate age to spay your pet, and will likely recommend that you wait until she is finished with her estrus phase to spay her.

At What Age Should I Spay My Dog?

Although veterinarians used to recommend as early as four months old to ensure she never went through a heat cycle and thus avoided mammary cancer, current research suggests that large- and should be allowed to grow before the hormones needed for skeletal development are removed. Before selecting when your dog should be spayed, discuss any health issues with your veterinarian.

  • How long does a dog stay in heat?

    Dogs are in heat for a week-and-a-half to two weeks, sometimes longer.

  • Can a dog get pregnant when not in heat?

    No, she cannot. Dogs can only get pregnant when they are in heat.

  • How do you keep the house clean when a dog is in heat?

    The best way to keep your house clean is to outfit your dog in a heat diaper, something that will catch the blood that she is discharging.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.


"Sato, Junko et al. Comparative Histopathology Of The Estrous Or Menstrual Cycle In Laboratory AnimalsJournal Of Toxicologic Pathology, vol 29, no. 3, 2016, pp. 155-162. Japanese Society Of Toxicologic Pathology, doi:10.1293/tox.2016-0021", "Sato, Junko et al. Comparative Histopathology Of The Estrous Or Menstrual Cycle In Laboratory AnimalsJournal Of Toxicologic Pathology, vol 29, no. 3, 2016, pp. 155-162. Japanese Society Of Toxicologic Pathology, doi:10.1293/tox.2016-0021", "Estrus And Mating In DogsVCA Animal Hospitals, 2020." ;