As birth rates among young women plummet, small dog ownership has risen rapidly in America’s urban centers. America’s next generation of youngsters should be called “Generation Rex.”If you’re wondering why playgrounds around the city are so quiet and dog runs are packed, a new report has an answer: More and more US women are forgoing motherhood and getting their maternal kicks by owning handbag-size canines.Data from the Centers for Disease Control and Prevention show that a big drop in the number of babies born to women ages 15 to 29 corresponds with a huge increase in the number of tiny...