Can a Dog Get Pregnant Out of Heat?

When it comes to a dog’s reproductive cycle and pregnancy, the birds and the bees are a little bit different from humans. It is important to understand how it all goes down if you have a dog who is not spayed in order to know what’s normal and what could be a possible medical complication. The female dog’s reproductive cycle is also called the estrous cycle and it has four distinct phases.

As a pet parent, you may not always be able to tell what phase of the cycle your dog is in. Proestrus and estrus tend to be the most obvious phases as this is what is described as being in heat. It is during these phases that dogs show physical changes like vaginal discharge and swelling of the vulva, along with behavioral changes that may suggest they are ready to mate.

Navigating life with a new pet? Head to littleKin!

littleKin™ is Kinship’s home just for puppy and kitten parents. Bop over to check out expert advice, new pet tools, and special deals—all curated for your newest family member.

Get Free Advice

There is a lot of variation in how long each phase of the cycle lasts and the exact signs that different dogs will demonstrate. Pet parents who are inexperienced with heat cycles may not always notice the subtle signs that their dog is in heat. It is important to keep female dogs who aren’t spayed yet away from male dogs who aren’t neutered yet.

Read on to learn all about the heat cycle in dogs.

Can dogs get pregnant when not in heat?

The short answer is no; dogs cannot get pregnant when they are not in heat. This is because dogs only ovulate during the phase of their cycle that people refer to as “being in heat,” also known as estrus. In order to get pregnant, they must release an egg and then mate within a short period of time to fertilize the egg.

If they were to mate at other times, no eggs would be present and no pregnancy would occur. Some confusion may happen when pet parents don’t realize their dog is in heat, or they misunderstand the timing of the cycle.  

Can a dog come into season without bleeding?

“Coming into season” is another term used to describe being in heat, or estrus. Typically, female dogs have the heaviest bleeding during proestrus, which is the phase that occurs right before estrus. Some pet parents may assume their dog is no longer in heat if they stop seeing vaginal discharge with blood in it. However, this may simply occur when they transition from proestrus to estrus, which is the phase where they can become pregnant.

Other dogs may have very subtle signs of heat and may not have vaginal discharge at all, or it may be such a small amount that it could be easily missed by an untrained eye. While this is more unusual, it does happen sometimes. And while we humans may be unaware of what’s going on, male dogs won’t miss the signs that she is in heat because they can sense changes in her pheromones and her willingness to mate during this time. Therefore, even if you don’t see signs that your dog is in heat, it is possible that she is, especially if male dogs are suddenly giving her lots of attention.

Related article

How to Tell If Your Dog Is Pregnant

And what to look for week by week.

What does “heat” mean in dogs?

Heat is a term used to describe the phase of a dog’s reproductive cycle when she shows both physical and behavioral signs of being ready to mate and can become pregnant. Many people use this term to describe the phases of proestrus and estrus but technically, estrus is when ovulation occurs, and dogs can become pregnant.  

Phases of the canine estrous cycle

There are four main phases to the dog’s reproductive cycle. Proestrus is the start of what people commonly refer to as being in heat. During proestrus, dogs start showing physical changes like swelling of the vulva and vaginal discharge with blood in it. This phase usually lasts about 10 days but can be highly variable.

After proestrus, dogs transition to the estrus phase where they become more receptive to mating attempts from male dogs and ovulation occurs. During estrus, vaginal discharge may no longer appear bloody, and may be more difficult to see at all. Dogs then move into the diestrus phase of their cycle where they stop showing interest in mating and many physical signs of heat begin to wane. They will stop having vaginal discharge and their vulva will no longer look enlarged. During this phase, they may show signs of mammary development even if they are not pregnant.

Dogs who are not pregnant will then move into the longest phase of the cycle, known as anestrus. During this phase, hormone levels continue to drop and physical and behavioral signs of heat are absent. This phase can last anywhere from four months to over a year before dogs return to the proestrus phase again. 

How frequently do dogs come into heat?

Most dogs come into heat about twice a year, or every six months if they do not get pregnant. However there is a lot of variation between individual dogs and even between certain breeds of dog. Some dogs may have more than two heat cycles in a year, while others may only have one or fewer. Over time, with careful tracking, pet parents may be able to get a sense of their dog’s average cycle length which can be helpful in predicting their next cycle. There are also tools veterinarians use to help track a dog’s cycle.  

Signs your dog is in heat

Dogs experience a number of physical and behavioral changes when they are in heat. Remember that signs of heat start with proestrus, which is the precursor to estrus, or the time they can actually get pregnant. During proestrus, most dogs will have swelling of the vulva and vaginal discharge that looks bloody.

They may also pee more often and show changes in their appetite and energy level. During proestrus, they may appear more friendly towards male dogs but will not allow them to mate. As dogs transition to estrus, their vaginal discharge often changes from appearing bloody to looking more clear. They will be much more attentive to male dogs and may even try to escape in order to get to a male dog. Male dogs will be very attracted to female dogs in estrus as well. During estrus, most female dogs will allow a male dog to mate but at other times in their cycle, they will not. 

Related article

Dogs in Heat: Signs, Stages, and Care Tips

Helpful tips to keep your dog safe and comfortable.

What is silent heat?

Silent heat is a term used to describe dogs that do not show external signs of being heat even though they are cycling through proestrus and estrus. This is uncommon but does sometimes occur. There are also other explanations for why a pet parent does not see signs of heat in a female dog. One possibility is that younger dogs may not have reached sexual maturity yet. Dogs have their first heat cycle anywhere from six months old to up to two years old, with larger dogs taking longer to reach maturity.

Another possibility is that a dog is not cycling regularly due to a medical problem. Dogs who are underweight or have a serious illness may not cycle. Additionally, sometimes pet parents do not know that their dog is already spayed. Dogs that are adopted as adults may not have medical records from their early life and may have been spayed years earlier, making it difficult to see a surgical scar. Finally, some dogs have more subtle signs of heat than others which may be difficult to spot.    

How to know if your dog is in silent heat

If you suspect your dog has a silent heat cycle, there will be no visible signs. You may notice male dogs suddenly paying a lot of attention to her and if they are near her, mating may occur. A veterinarian can also diagnose this by tracking the phases of her cycle. This includes tests like vaginal cytology, or looking for different types of cells in the vagina that are only present during estrus. They can also use blood tests to measure progesterone levels over time as this hormone level rises at predictable points in their cycle. 

Bottom line:Dogs cannot become pregnant when they are not in heat 

Not every pet parent realizes when their dog is in heat, or when they are most likely to get pregnant in their cycle which can lead to confusion and/or unexpected pregnancies.

Some dogs may not show obvious external signs of heat even when they are in the estrus phase of their cycle and can still become pregnant.

FAQs

What age do dogs have their first heat?

The age for a dog’s first heat cycle can be anywhere from about six months old to two years old. Smaller dogs tend to reach sexual maturity sooner than large and giant breed dogs. 

How long does a dog’s heat/season last?

This is very variable. Most dogs will be in the proestrus and estrus phases of their cycle for about 20 days but it can be as long as 50 days. 

How long does a dog in heat bleed?

There is no exact time frame for when dogs will have vaginal discharge during their cycle but this is usually heaviest during the proestrus phase, which lasts about 10 days. For some dogs, it may be longer, while other dogs may not have any obvious vaginal bleeding.

When can your dog get pregnant after bleeding?

Dogs ovulate during the estrus phase of their cycle, which usually occurs right after the heaviest bleeding stops and their vaginal discharge starts to look more clear. If they do not get pregnant in that window of time, they will usually not go into heat again for about six months or longer. 

References

• “Dog Estrous Cycles,” Cornell College of Veterinary Medicine Canine Health Topics, July 2023. 

• Kowalewski, M., “Advances in understanding canine pregnancy: Endocrine and morpho-functional regulation,” Reproduction in Domestic Animals, vol. 58, no. S2, September 2023, pp. 163-175.

• Lawrence, J., “Abnormalities of the Estrus Cycle,” Clinical Theriogenology, vol. 10, no. 3, September 2018.