The woman was arrested and charged with vehicular homicide after a fatal hit-and-run accident in May this year.
A 58-year-old motorcyclist died after the woman hit him while driving a camper van, and she was being held in a section of Turin's Le Vallette prison for mothers with young childr She had reportedly been stopped by police six times previously for driving without a license.
On Monday, the prison guards' trade union OSAPP said the 22-year-old inmate had escaped - leaving behind her daughter, who is just a few months old.
According to the statement from the union, the woman made her escape at around 3:30pm, by opening a gate into a courtyard where there was a children's play area, and fleeing on foot into the fields. A guard tried to follow her but was unable to track her down.
Social services are taking care of the baby girl.
Jailbreaks have happened before in Italy's prisons - with ropes made of knotted bedsheets a particularly common escape tool.
Last year, three prisoners - including one convicted killer - fled through the window of Rome's Rebibbia jail using their bedsheets. After this incident, 14 prison officers, including its former director, were investigated for security breaches.
They were accused of "omission of due care" and failing to fix problems which had been discovered after two other inmates had used the same escape method previously.