On average, the length of time between the birth of puppies from the same litter is from 30 to 60 minutes. According to the American Kennel Club, more than two hours elapsing between puppies warrants a call to the veterinarian.
If a dog is straining and having strong contractions, a puppy usually emerges within 30 minutes. If more than 45 minutes elapses while the dog is having strong contractions and is straining, a call to the veterinarian is necessary. Once each puppy is born, it is necessary for an afterbirth to be released. Retained afterbirth might hinder the birthing of the remaining puppies.