The mother of the country's only giant panda twins has delivered another pair of cubs in Zoo Atlanta on Saturday.

Lun Lun was impregnated via artificial insemination on March 28th. If Lun Lun's second set of twins survive, they will be her sixth and seventh cubs.

Newborn pandas are very vulnerable. They are about the size of a stick of butter. They can grow to up to 330 pounds. Three years ago, the mother bear Lun Lun gave birth to female cubs Mei Lun and Mei Huan. The two are still at the Georgia zoo. China owns the two pandas and could have them back this fall.