Zoo vets: Evidence suggests mom of giant panda is pregnant again

WASHINGTON -- Officials at Washington's National Zoo say they believe the mother of nearly 2-year-old giant panda Bao Bao is pregnant again.

The zoo said veterinarians performing an ultrasound Wednesday on panda Mei Xiang detected what they believe is a developing panda fetus.

The zoo says that based on the size of the fetus, veterinarians think Mei Xiang could give birth early next week or possibly in early September. But the zoo says there is a substantial possibility that Mei Xiang could miscarry or not give birth.

"Today, we are cautiously optimistic," said Dennis Kelly, director of the Smithsonian's National Zoo. "We want a healthy cub for all the right conservation reasons. I am excited, but I have to say that we were prepared for a cub even before this morning's ultrasound. Our expert team of keepers, scientists and veterinarians are going to do exactly what they are trained to do and I'll just ask everyone to remain positive with us."

Though Mei Xiang has given birth to cubs in the past, the zoo says historically she has refused to participate in ultrasounds at this stage.

Mei Xiang's first surviving cub, Tai Shan, was born in 2005. Bao Bao, her second, turns 2 on Sunday.

As CBS News correspondent Chip Reid reported, Mei Xiang spends most of her time these days sleeping, curled up on her right side, sometimes on her left and even sprawled out on her stomach. It's also how zoo keepers think they know Mei Xiang just might be pregnant.

"Other pandas, we can always call them out with a fruitsicle or some honey, but when Mei Xiang is in this mode, there's nothing we can do to get her to move," Brandie Smith, who is in charge of animal care, said.

Mei Xiang was artificially inseminated twice in April. One of the potential fathers is in China; the other is Tian Tian, a male panda at the National Zoo.