It has previously taken months before Mei Xiang's cubs have been introduced to the public.
AP news agency reports that her first cub, Tai Shan, was born in 2005 and returned to China in 2010; her second cub, Bao Bao, is two years old on Sunday and still lives at the zoo.
The panda population is threatened by habitat loss as land is increasingly inhabited by humans, with about 1,800 pandas left in the wild in China.
However, the number living in the wild in China has gone up over the last 10 years.