So-called "teacup" Yorkshire terriers don't fit the American Kennel Club breed standard for this toy dog. Generally, the smaller the breed, the fewer puppies born in each litter. Because of the health problems inherent in teacup Yorkies, breeding them is a bad idea.
Also known as tiny or miniature Yorkies, teacup Yorkies result from the breeding of undersized, or runt, Yorkshire terriers. These exceptionally small Yorkies often suffer from fragile bones, hypoglycemia, collapsed tracheas and other health issues. Responsible breeders do not deliberately create teacup Yorkies.
Yorkshire terrier litters generally range from two to five puppies, with an average of 3.3, according to a study cited by the AKC. That figure is based averaging the size of more than 53,000 Yorkie litters. Another toy dog breed, the Chihuahua has the same litter range and average. Unless you have canine delivery experience, it's best to arrange for your Yorkie to deliver her puppies at a veterinary hospital. That's especially true if the expectant mother is a teacup Yorkie.