WASHINGTON -- Could a sibling be on the way for the National Zoo's star attraction, Tai Shan?

The zoo's giant panda cub was born in 2005 after his mother, Mei Xiang, was artificially inseminated.

Mom went through a revolutionary artificial insemination again this week, receiving one injection Wednesday and another Thursday.

Slideshow: Giant Panda Artificially Inseminated
Tai Shan Slideshows: Playing In Sun | Playing In Snow | First Steps | Naming Ceremony | Panda Progression | More Pictures | Panda Press Day

Two years ago, Mei Xiang was artificially inseminated with the sperm of Tian Tian. But reproductive specialists said it was time to diversify the captive giant panda population, so they turned to male giant panda Gao Gao at the San Diego Zoo.

It's the first time scientists have exchanged sperm between zoos in North America.

Scientists took 17 straws of sperm from Gao Gao and then froze the sperm for transport using a revolutionary freezing method that can preserve sperm for two weeks time.

"This is the first time this freezing-thawing technique was used anywhere in the world," Dr. Carlos Sanchez said.

Reproductive specialist Dr. Copper Aitken-Palmer explained why a new partner was picked for Mei Xiang.

"Gao Gao has not had very many cubs, so we wanted to make sure he kept having cubs, and he's ranked high genetically to have more cubs," Aitken-Palmer said.

Giant Pandas can only get pregnant once a year during a specific 48-hour period. This week, the timing was perfect.

"The egg is released from the ovary. It's perfect timing," said reproductive specialist Dr. Jo Gayle Howard. "It's sitting in the reproductive tract ready for the sperm to fertilize. ... We're very hopeful."

The total time of the actual insemination? One hour and 35 minutes.

Now it's a waiting game to see if Mei Xiang is pregnant or not. It could take three to six months to find out. Her hormone levels will remain high regardless. Veterinarians will use an ultrasound to make an accurate determination.