Police from the German state of Lower Saxony said they think the baby boy was born to the single woman in November 2007, but aren't sure if the baby was stillborn or alive when it was abandoned - a question which will have significant legal ramifications. Authorities said advanced decomposition has complicated the autopsy examination.
The corpse of the infant was found on Saturday wrapped in a towel and tucked into a sports bag some 50 metres away from a forest trail. Evidence found at the site led police to the young woman, they said Monday.
The suspect was subject to prolonged questioning about details of the incident and possible motives, police said.
In an unrelated case, police determined this week that a dead baby girl found by hikers in a wooded area near Berlin's Müggelsee lake was killed shortly after birth. Further investigation is pending.
A German appeals court on Monday also confirmed a 15-year prison sentence handed to a another woman for killing eight of her newborn babies in the country's worst post-war infanticide case. The court in Frankfurt an der Oder in eastern Germany found that the fact 42-year-old Sabine Hilschenz was an alcoholic did not reduce her accountability for the crime.