Female dogs that have not been spayed are capable of reproducing and giving birth to puppies. This is often a desirable thing for dog breeders, but might otherwise be unfavorable for owners of unspayed dogs who are worried about having too many puppies on their hands. Overall, dogs can only get pregnant when they are in heat, which does not happen very often.
For dog owners who are hoping to breed puppies, paying attention to their female dog’s heat cycles is crucial for success. On the other hand, if you have an un-spayed puppy or older female that you do not want to get pregnant (for whatever reason) it is in your best interest to keep them away from male dogs that haven’t been neutered when the female is in heat.
Can a dog get pregnant when not in heat?
When a dog is “in heat,” it refers to their natural reproductive cycle. When female dogs are not spayed, they still have all of their reproductive organs and will therefore go through this cycle. Being in heat means that the dog is ovulating and her body is preparing to become pregnant, whether or not a male dog is around to fertilize their ovaries.
Much like humans, ovulation is essential for pregnancy. As such, it is only when your dog is in heat that they can become pregnant. If your female dog is not in heat, then they cannot get pregnant. Most breeds of dogs will go into heat every six to eight months or so, but larger dogs will sometimes only have one heat per year.
If you think your dog might be in heat, it’s a good idea to check with your veterinarian to confirm her symptoms. When a dog is in heat and left alone with a male dog that has not been neutered, chances are that they will attempt to reproduce and the likelihood of your dog becoming pregnant are very high.
However, if you are certain that your dog is not in heat, you will be able to allow them to mingle with un-neutered male dogs without the possibility of pregnancy. As mentioned previously, if your dog is not in heat (i.e. not ovulating), there will be no ovaries available for fertilization and therefore no chance of them getting pregnant.

How do I know if my dog is in heat?
Whether you are trying to breed dogs or avoid a pregnancy, it’s important to understand be able to accurately identify the symptoms of a female dog in heat so that you can care for them accordingly. For most breeds of dogs, there is no specific time of year that corresponds with them being in heat, so it’s smart to track previous heats so you can predict the next one.
Younger dogs will often have a very irregular reproductive cycle, similar to human females first going through puberty. It can usually take about two years for a dog’s heat to become more regular and predictable, so it’s important to pay attention to your dog when it is young and might possibly go into heat.
Common symptoms of a dog in heat include: bloody discharge, swollen nipples, a raised tail, and increased urination. Female dogs in heat will also exhibit an increased interest in male dogs, sometimes with an enthusiasm that seems fairly uncharacteristic. This is part of the natural instinct in all animals to procreate.
In short, the reproductive cycle of a female dog can be exhibited via a variety of symptoms, which might differ from cycle to cycle. Thus, it is important to be able to know when your dog is in heat, as this is the only time when they can get pregnant.