Surgeons in Shanghai are to go ahead with the operation on a baby boy born with three arms.
Doctors had been unsure which of the boy's two left arms should be removed as they were both well developed.
However they have decided to remove the one growing closer to his chest and the operation will go ahead on Tuesday.
But the boy, Jie-jie, will require long-term physical therapy because the hand on the arm that will remain does not currently appear to function.
JIE JIE'S DIAGNOSIS
1. Smaller arm at front of body will be removed. Tests have found that it is less developed
2. Left arm is in normal position, but does not move unless pulled and does not have a palm
3. Jie Jie has only one kidney and may also have problems that could lead to curvature of the spine
Surgery expected to last 3-5 hours
Biggest risk will be damage to nerves and blood vessels in shoulder
Jie-jie, who is in a stable condition in the intensive care unit, was born on 1 April at a small hospital in Anhui Province.
He cries when either of his left arms is touched, but smiles and responds normally to other stimuli.
The arm closer to the body, which will be removed, is very slim and is always bent.
The other one is normally shaped but does not move unless it is pulled, and does not have a palm.
He is also reported to have just one kidney, and may have problems that could lead to curvature of the spine.
Dr Chen Bochang, head of the orthopedics department at Shanghai Children's Medical Center said: "The biggest difficulty here is from the risk of damage to nerves and blood vessels in the shoulder."
He added he was optomistic about the surgery which is expected to last from three to five hours.
Other children have been reported born in China with additional arms or legs, but in all those cases it was clear which limb was more developed. The hospital is one of China's most experienced in dealing with unusual birth defects, including separating conjoined twins.