(NewsNation) — French bulldogs are the most popular breed in the United States, according to the American Kennel Club.

America’s new favorite dog ended the labrador retriever’s 31-year run, but now, the popularity of French bulldogs has caused people to worry that demand for them will encourage unethical breeders.

Dr. Bruce Smith, a professor at the Auburn University College of Veterinary Medicine, said the French bulldog’s new designation is both “good news” and “bad news.”

“With the popularity, the dogs become more available, and more people will be breeding them, and there’s going to be a big demand for them,” Smith told NewsNation’s Mitch Carr on “Morning in America.” “But the other side of the coin is that with big demand comes unscrupulous breeding. And sometimes, that leads to more defects being present in the gene of the dog.”

French bulldogs are a kind of canine known as brachycephalic, or “flat face” breeds. Some breeders, though, try to get these dogs to have a flatter and flatter face, to the point where they don’t have much of a nose anymore, Smith said.

“It really has a lot of difficulty breathing, it also affects the soft palate,” Smith said. “So those dogs snore… they have trouble with hot weather or humid weather as well.”

If you’re thinking of buying from a breeder, here are some things Smith says to keep in mind:

• Do not buy from a pet store. If you want a purebred dog, going to a breeder or breed rescue is a “great idea,” Smith said.
• When looking to buy a purebred dog, in particular, you should be able to talk to the breeder, Smith said. “You should be able to see the mother,” he said. “Dogs should be on site.”
• Be wary of those breeding more than one kind of dog.
• Look at the condition of the dogs. “You want to be able to see the mother dog before you buy that puppy,” Smith said.
• Make sure the pups are happy, healthy, that their coats are clean, and that their tails are wagging. Or, in the case of French bulldogs, “their little stumps,” Smith said.