The woman made the confession to her gynaecologist, who then notified police. Investigators discovered the baby's body in the bathtub of the woman's apartment in the Bremen district of Schwachhausen.
An autopsy will be conducted on the child, who is thought to have been born last Tuesday, to determine the cause of death.
The mother has been taken into custody and prosecutors have launched an investigation.
A police spokesperson said no further details are known at the present time.