In surprise twist, D.C. panda gives birth to twins

The Smithsonian National Zoo welcomed its newest member Saturday afternoon, but it wasn't long before a second addition would come along.After giant panda Mei Xiang gave birth Saturday afternoon to a cub that zoo officials have described as "showing all signs of being healthy and happy," there was an unexpected twist. Mei Xiang then gave birth to another panda about five hours later.Giant pandas have twins about half of the time and this is the the third time a giant panda living in the U.S. had had twins, according to the National Zoo. The twins are the first giant pandas to be born in the United States this year.