A final scan has revealed that Huan Huan, who is on loan to Beauval zoo in central France from China with her male partner Yuan Zi, is expecting twins on Friday or Saturday.
The impending birth will be the first of a panda in France.
It was announced with great fanfare on July 26 after a first scan, which appeared to show the nine-year-old bear — who arrived in Beauval in 2012 after intense, high-level negotiations between Paris and Beijing — was carrying a single cub.
But on Tuesday veterinarians assisted by two Chinese panda reproduction specialists noticed a second foetus.
“The problems are only just starting!,” the zoo's director Rodolphe Delord joked.
His sister Delphine Delord, the communications director, acknowledged that the situation would be “fragile”, with mothers often known to abandon the second cub.
“We're doing everything possible to ensure it goes well,” she said.
Huan Huan's carers will place the second cub in an incubator and rotate the tiny bears every two hours with their hundred-kilo mother, Beauval's head veterinarian Baptiste Mulot said.
Breeding pandas is notoriously difficult.
The female panda is only in heat once a year for about 48 hours. The gestation period for pandas is a mere 50 days.
Huan Huan (meaning “happy”) and Yuan Zi (“chubby”) are the only giant pandas living in France.
The pair were brought together in February, in the hope they would mate, but it didn't happen. In the end, the zoo performed an artificial insemination.
If all goes well with the birth, the cubs will leave Beauval in the next two to three years to be returned to China.