The youngster from Karachi in Pakistan was believed to have had a parasitic twin, which had not developed properly in the womb, resulting in the extra legs.
A team of five doctors had fought to save the boy’s life at the National Institute of Child Health in Karachi.
The head of the NICH, Jamal Raza, said the abnormal birth was the result of a genetic disease which would affect only one in a million or more babies.
“It was strange that apparently an abnormal baby with six legs was as normal as other children,” he said.
Before surgeons could operate they said they had to work out which of the limbs belonged to the boy and which to his twin.
Doctors examined MRI, blood tests and CT scan reports before deciding to perform the surgery. The operation lasted eight hours and was performed in stages.
The baby had been in an intensive care unit ward since he was born last week to the wife of an X-ray technician.
Imran Shaikh, the baby’s father who lives in Sukkur, said he was grateful his son was treated.
“We are a poor family. I am thankful to the government and doctors for helping us successful operating my baby,” he said.