Three weeks after a giant panda cub was born at the San Diego Zoo, veterinarians confirmed on Thursday that the newborn is a girl.
"The veterinary staff had its suspicions during the cub's first exam last week but chose to wait one more week to get a second look," the zoo said in a written statement.
The cub -- who in keeping with Chinese tradition won't be named until she is 100 days old -- now weighs 22 ounces (618 grams) and is 11.6 inches (29.5 cms) long from the tip of the nose to the base of the tail.
The cub is only the second giant panda cub to be born in the United States this year and one of the few of the endangered species in captivity to be born naturally. A male was born at Washington's National Zoo last month.
Thirteen-year-old mother Bai Yun, on loan from China, was originally carrying twins but one of the fetuses died in the womb. Giant pandas are notoriously difficult to breed because they are normally solitary creatures and the female is fertile only 3-5 days a year.
Under the agreement with China, the new cub will be sent to China when it is 3 years old.