Look for pregnant dog symptoms if your dog is not spayed and her behavior starts to change. It helps to know the four stages of the heat cycle, as your dog may also have a false pregnancy, which can happen during one of the stages.
What are the stages of heat?
Proestrus, which is the first stage, is the increased follicular activity of the ovary. Estrus, the second stage is where the bitch is receptive to males and will let males mount her. Diestrus, the third stage, is where the corpora lutea produces progesterone, and the bitch will be non-receptive to males. Anestrus is the fourth and longest stage because it is when your dog gets a break before going into heat again.
Why does knowing the heat cycle matter so much?
Knowing the cycle can help you narrow down the likelihood of your dog being pregnant. If you are not planning a pregnancy, you must keep your bitch sequestered during the first three stages of the heat cycle. Male dogs know when a female dog is in heat, and if your dog gets loose, she will encounter a male dog, and chances are good that she will get pregnant.
I was good about keeping my dog inside, but she's still acting strangely. What's going on?
Sometimes, a dog may exhibit pregnancy symptoms, even if there is no way she could be pregnant. This may be a false pregnancy, and you should go to the vet, whether you think she got out of the house or not. A false pregnancy can also have complications, such as pyometra, in which pus builds up in the dog's uterus. If you have dog health insurance, check your policy. While the insurance does not always cover dog pregnancy, it may cover problems resulting from a false pregnancy.
I think the dog got out. What signs should I watch out for?
If your bitch does happen to get pregnant, the earliest you can tell is about 16 days with an ultrasound test. Sometimes the ultrasound will not pick anything up until the 18th through 20th days. Usually, by the time day 25 hits, you can hear fetal heartbeats with a stethoscope. If this is an unplanned breeding, you would not notice the pregnancy, nor would the average person request an ultrasound. If you start seeing the bitch's behavior changing, you should request an ultrasound.
Also, the bitch may become overly affectionate, to the point of demanding the affection. This is not always the best way to tell if your bitch is pregnant, though, as some bitches simply want to be left alone. Her nipples will start to swell, and during the first days of the pregnancy, she might have a decreased appetite and may be lethargic.
During the later stages of the pregnancy, the bitch may seem like she's very hungry and is ready to eat you out of house and home. Allow her to eat what she wants (within reason), as she is now feeding quite a few little puppies. Depending on the breed and your bitch's lines, she may produce one to more than ten puppies in the litter. Her stomach area will also start to harden, and you may even be able to feel the puppies as it gets closer to her due date.