Atlanta ? A giant panda has given birth at Zoo Atlanta.

Lun Lun delivered her first cub just before 5 p.m. Wednesday, according to a zoo spokeswoman.

Zoo keepers were watching to see whether the baby panda, estimated to weigh four ounces, had a twin, according to the Atlanta Journal-Constitution. Half of panda births result in twin cubs.

Zoo Atlanta artificially inseminated the 8-year-old Lun Lun at the end of March with semen taken from her partner, Yang Yang. They had tried for 7 years to successfully mate the pair naturally.

Only four giant pandas have been born and successfully raised in a U.S. zoo. A panda cub at the National Zoo in Washington, D.C., born last summer was also the product of artificial insemination.