Chihuahua puppies are born after a 63 day gestation period and the average litter contains one to three puppies. Larger litters are possible, but during pregnancy Chihuahuas must be monitored closely because they often require C-section deliveries due to their small stature. Like all dogs, Chihuahuas are born with their eyes closed and generally open them after a week or two. They require little care from humans, provided the mother is nursing and grooming them, until they are several weeks old.

Chihuahua puppies are born with flat ears. Most ears stand-up, as per the breed standard, by the time the puppy is 1 year old, but some ears remain flat, making the dog ineligible for dog shows.

The Chihuahua is the smallest dog breed in the world. At maturity, a Chihuahua should weigh between 2 and 7 pounds, according to the American Kennel Club breed standard. They are generally a healthy breed and on average live 12 to 20 years. Long-coat and short-coat Chihuahuas are recognized by the AKC.

Chihuahuas have a complex personality and can be difficult to train. They are extremely loyal to their owners and make great companion dogs. They can be strong-willed and should not be left unsupervised around small children.