How Long Does The Whelping Process Take?

The first stage of labor lasts on average 6-12 hours.  This is when dogs start having uterine contractions, pant, pace, become restless, stop eating, vomit, and seek a place to nest.  Stage 2 begins when the cervix is fully dilated and the first puppy moves into the cervical canal--at this point uterine contractions are very intense and can be observed.  The first puppy should be born within 4 hours of the start of Stage 2.  The time between puppies is usually 20-60 minutes but can last 2-3 hours.  
Your dog needs to be seen by a veterinarian immediately if persistent, strong contractions last 30 minutes with no puppy, more than 4 hours from the start of Stage 2, more than 2-3 hours between puppies, or failure to deliver after the body temperature falls below 99 degrees Fahrenheit.
If you have any concerns your dog is having a difficult or problematic labor get her to a veterinarian immediately!  Dystocia (difficult birth) can be fatal to mother and puppies--it is an emergency.