One of the most asked questions that I have answered is how to tell if a dog is in labor. This is usually asked by people that are first time female dog owners and they thought their dog had been kept away from others just enough to not get pregnant.
Take your dog's rectal temperature. When your dog's temperature drops to 99 degrees and below, your dog will go into labor within 24 to 48 hours.
Notice if your dog is refusing to eat or is restless. These are generally good indicators that your dog is in labor or going into labor.
Note if your dog is producing milk or you see a thick mucous discharge. Both of these are signs of labor.
Watch to see if your dog seeks out a quiet spot. Dogs prefer a protected quiet place to have their puppies.