The baby was found two hours after her disappearance sparked a major police search in the western Swedish city.
The woman, aged in her 40s, was detained on Tuesday afternoon and questioned by police on Wednesday. Police said that the woman was under the influence of drugs and alcohol to such an extent on Tuesday that she was unable to undergo questioning then.
She was kept in police custody overnight on a 'reasonable degree' of suspicion (the lower degree of suspicion according to Swedish law).
"She admits that she handled the pram but denies the crime," her lawyer, Hans Billeskans, told TT.
The baby's mother told police she had left her in the pram outside a kindergarten in the Hisingen area of Gothenburg while she went inside to pick up her older child. When she came back outside five to ten minutes later, the baby and the pram were gone.
Police launched a major search operation and called in extra resources, including police dogs and a helicopter.
The baby was found in good health two hours later, when a member of the public reported seeing the pram outside a shop several kilometres away from the kindergarten.