The woman, whose identity was not released, was apparently present during the two-hour rescue, but did not reveal she was the mother until police confronted her.
According to state-run newspaper Dushikuaibao, police found baby toys and blood-stained toilet paper in the woman's rented room in the building where the rescue happened. Chinese media reported that the woman told police she couldn't afford an abortion and secretly delivered the child in the toilet.
She reportedly said she tried to catch the baby but he slipped into the sewer line. When she couldn't pull the baby out, she alerted her landlord. Authorities were called to the scene.
Firefighters located the baby in an L-shaped section of the pipe. They cut out the section and carefully dismantled it, freeing the baby boy, who greeted the rescuers with cries.
The baby weighed 6 pounds, 2.8 ounces and was taken to a hospital with minor injuries, according to local reports. It was not immediately clear whether the mother would face criminal charges.
The Associated Press contributed to this report.