If your female dog is not spayed, she will go through regular reproductive cycles known as heat cycles (also called estrous cycles). During this time, she can become pregnant if bred by a male dog.
Unlike cats, dogs typically go into heat only a few times per year.
How Often Do Dogs Go Into Heat?
Most female dogs go into heat approximately every 6–8 months, although this can vary depending on breed, age, and individual factors.
Some small-breed dogs may cycle as often as every 4–6 months, while giant-breed dogs may only cycle once every 10–12 months.
Most healthy adult dogs experience one to two heat cycles per year.
At What Age Do Dogs Start Going Into Heat?
Dogs typically experience their first heat cycle between 6 and 12 months of age, although timing varies by breed and size. Small breeds may enter their first heat as early as 4–6 months of age. Large and giant breeds may not experience their first heat until 12–24 months of age.
A female dog can become pregnant during her first heat cycle.
What Are the Stages of the Canine Heat Cycle?
The canine heat cycle has four stages:
Proestrus (7–10 days)
During this stage, the vulva becomes swollen, and a bloody vaginal discharge is present. Male dogs are attracted to the female, but she is usually not receptive to mating.
Estrus (5–14 days)
This is the fertile period. Vaginal discharge often becomes lighter in color, and the female becomes receptive to mating. Pregnancy is most likely during this stage.
Diestrus (About 60 days)
Hormone levels change, and the reproductive tract returns toward normal. This stage occurs whether or not the dog becomes pregnant.
Anestrus (Several Months)
This is the resting phase between heat cycles.
Signs Your Dog Is in Heat
Common signs include:
- Swollen vulva
- Bloody or pink vaginal discharge
- Increased urination
- Attracting male dogs
- Changes in behavior or temperament
- Increased affection or clinginess
- Restlessness
- Tail held to one side when approached by male dogs
Every dog is different, and some signs may be more noticeable than others.
Can Dogs Become Pregnant During Heat?
Yes. Female dogs can become pregnant during the estrus phase of their heat cycle.
Because the fertile window may vary among individual dogs, it is important to keep intact females separated from male dogs throughout the entire heat cycle if pregnancy is not desired.
Benefits of Spaying
Spaying eliminates heat cycles and provides several health benefits:
- Prevents unwanted pregnancies
- Eliminates heat-related bleeding and behavioral changes
- Prevents uterine infections (pyometra)
- Reduces the risk of mammary (breast) cancer when performed early in life
- Helps reduce pet overpopulation
Your veterinarian can help determine the best timing for spay surgery based on your dog’s age, breed, and health status.
When Should I Contact My Veterinarian in Novato, CA?
Contact Center Veterinary Clinic if:
- Your dog’s heat cycle seems unusually long or frequent
- You notice excessive bleeding or discharge
- Your dog appears lethargic, ill, or uncomfortable
- You suspect your dog may be pregnant
- You would like to discuss spaying or reproductive health
Our team is happy to answer questions about your dog’s heat cycle, pregnancy prevention, and the best timing for spay surgery. Reach out to us today!