You can keep an eye out for certain signs that might help you identify if your Frenchie is pregnant although it may be tricky since shifting hormones can cause behavioral changes that range from one extreme to the other.
If your pooch is pregnant he or she might have a loss of appetite and begin to vomit. As an alternative she might start eating more than usual and she might become pickier about what she eats.
Your Frenchie will likely have less energy and you'll probably find that she sleeps more than usual.
You may have a harder time detecting this if shes a dog who lazes around a lot. If so you might want to watch how quickly she gets tired when walking as an indication that she might be pregnant.
You might notice a change in her behavior and a break from her usual routine. Its possible that she'll try to get more attention than usual.
In contrast to what you would expect she may follow you around or sit by your side more than usual.
As she changes hormones she may spend more time by herself and become agitated if too much attention is paid to her. You also need to be aware of other physical symptoms. During pregnancy a dogs nipples will grow larger than usual. Nipples (areolas) should swell a bit and may also become darker red than normal.
Also your Frenchie is likely to gain some weight particularly around the stomach area but this usually occurs once she is well into her pregnancy already. Your dog may begin to exhibit nesting behavior toward the end of her pregnancy.
When the pups arrive she might move her bed around to create a better nesting environment and become very grumpy and isolate herself. If you have noticed the odd behavior at this stage you should have visited your veterinarian.
Even though these signs can be helpful in identifying if your dog is pregnant the closest thing to knowing for sure is an ultrasound.