The following day, she and her boyfriend, James Hamilton, dumped the boy's body in the Ohio River.
Hamilton is charged with abuse of a corpse and tampering with evidence, but not charged with murder.
The 6-year-old's body is yet to be found.
In a press conference, Middletown police chief David Birk said the mother is "not showing much remorse at this time".
"She's not showing much remorse at this time, but she has confessed.
"No 6-year-old deserves this."
The officer also said that there were "red flags all over" from the beginning, as the mother and the boyfriend's statements contradicted each other from the start.
Two other children living in the couple's home have since been removed.
Middletown is a city about 61km north of Cincinnati.