Instructions
Check for an umbilical cord. For the first two or three days the pup will still have part of the umbilical cord attached. If the pup has been just recently born, the umbilical cord will be soft and pliable. If the pup is a day or so old the umbilical cord will be dry.
Look at the puppy's eyes. Newborn puppies are blind and their eyes will be closed. The pup's eyes will open between 12 and 15 days old. If the puppy's eyes appear swollen before they open, take it to a vet because and eye infection may be present. It can take up to 3 to 4 days for a puppy's eyes to completely open. Never try to force a puppy's eyes open. The eyes should initially be a bluish color and will change to their adult color over time.
Observe the puppy's movement. Newborn pups can't walk and can barely crawl. Puppies will crawl well between 7 and 14 days of age. Puppies should be able to walk at about 16 days of age and will have a normal gait at 21 days. Pups this stage will begin trying to explore.
Look in the pup's mouth. Newborns will have no teeth. Teeth will begin appearing at about 3 weeks of age and 4 weeks a puppy will hold toys in its mouth and play with litter mates. The pup will develop all of its deciduous teeth by about 8 weeks of age and then be able to eat solid food on its own.
Listen to the sounds the puppy makes. The newborn pup will have no form of vocalization except soft whines and cries and will be unable to hear. The puppy's ears began opening at about 14 to 17 days old and they should begin to hear clearly at about 4 weeks old. Puppies will begin to vocalize more at this stage. At 3 weeks of age the pup will wag its tail, growl, bare its teeth and begin to bark.
How to Determine the Age of Newborn Puppies
Dogs, like humans, are a species that develops slowly after birth and are incapable of surviving on their own as newborns. Being able to determine their closest approximate age will aid in helping them through this tenuous stage following birth. Since different breeds of dogs are different sizes at birth, size and weight are not viable means to determine the age of a newborn pup. Puppies will show specific signs of development at various stages.