The gestation period for a dog ranges from 56 to 69 days, with 63 being the average. While it's mostly a matter of waiting for nature to take its course, there are a few signs that will let you know when your dog is about to go into labor.
Temperature
About a week before your dog is due to give birth, or on day 55, take your dog's temperature on a daily basis using a rectal thermometer. If you don't know how to safely take your dog's temperature rectally, check with your veterinarian. Take her temperature at the same time every day, and make sure she has not been playing or running around just before you take her temperature. Her normal temperature should be between 101 and 102.5 Fahrenheit. It will drop to 100 degrees about 24 hours before she goes into labor.
Early Labor
Most dogs experience between six and 12 hours of early labor before finally giving birth. During this time, your dog may be restless, pant heavily, shiver and act uncomfortable. She may build or rearrange a nest for her puppies, and whine, retch or refuse to eat. Expect puppies within 12 hours of the start of this stage.