Panda cub born at San Diego Zoo

A 20-year-old giant panda has given birth at the San Diego Zoo, and it's a record. Officials say it's the sixth cub born at the zoo to Bai Yun, the most at a breeding facility outside of China. Zookeepers and researchers watched the birth on July 29, 2012, via a closed circuit camera mounted inside the birthing den. In a blog post, zoo officials say Bai Yun immediately scooped the cub into her arms and comforted the newborn. Because of Bai Yun's advanced age the pregnancy was considered high risk, but zookeepers say mother and baby are doing fine. The sex of the cub won't be known for several months. Bai Yun is seen here in an undated photo provided by the San Diego Zoo.

One of the tools the staff used to monitor Bai Yun's pregnancy was ultrasound. Here, in this ultrasound image, it is possible - if you know what you're looking for - to see evidence of the in-utero cub.

San Diego Zoo veterinarian Meg Sutherland-Smith points to the ultrasound to indicate the panda fetus.

This is Yun Zi, Bai Yun's 3-year-old son, who's still at the San Diego Zoo but may soon be sent back to China under an agreement that says that China has the right to claim any three-year-old pandas born outside the country.

This is Gao Gao, the 20-year-old male who is father to Bai Yun's new cub, as well as Yun Zi.

Gao Gao keeps himself busy early in the morning at the San Diego Zoo.

The panda staff gathers around Bai Yun as they give her an ultrasound, away from any unfamiliar faces that could have stressed the panda out.