A dog's gestation period lasts about 63 days, regardless of breed, according to the American Kennel Club. A dog who is pregnant will typically be evident with an increase in its appetite, thereby also increasing its weight. Nipple size can also increase.
A veterinarian can confirm pregnancy in dogs at around 28 days gestation through various ways, such as performing an ultrasound, taking an X-ray or doing an abdominal palpitation. Increased feeding is not necessary for pregnant dogs until the 5 weeks before the whelping stage, or as weight increases. This increase in food should be gradual, as sudden larger meals can cause discomfort for the dog, especially for Yorkshire Terriers, which are a small breed.
Dogs typically begin to decrease their appetites or actually stop eating just before going into labor. A ready dog may also build a "nest" where she plans to give birth. Around 24 hours after the dog's temperature drops to approximately 99 degrees Fahrenheit or lower, she can be expected to enter the first stages of labor. During these first stages, the dog will appear to breath heavily, appear restless and strain. Puppies are then born in individual sacs that are removed before the puppy can breathe. As complicated as the process may see, most dogs can give birth on their own without human intervention, as stated by the American Kennel Club.