Police in Washington Park, a village next to East St. Louis, said the girl reported that she was raped by her captor, got pregnant and had a baby.
In April 2010, St. Louis, Mo., police listed the girl as a missing or runaway juvenile. She was 15 when she disappeared.
She escaped from the home in Washington Park earlier this week and went to police, saying her child was still in the house.
About two dozen members of a SWAT team swarmed the home Thursday afternoon, recovered the child and arrested a 24-year-old man.
Washington Park Police Chief David Clark said it appears the man's mother assisted in the crime. She was also taken into custody. Police would not identify either of them by name because they had not been charged as of Thursday evening.
The teen told police she was held against her will and was beaten and sexually assaulted almost every day. She reported trying to escape several times but told police that her captor chased her down each time and forced her back to the home at gunpoint.
She told police she was able to escape this week with the help of a relative.
Police said the teen also told them she was forced by the man and his mother to give a false name in medical records during her pregnancy and when the child was born.