The infant was left at a health centre and the mother has been taken to hospital after sustaining leg injuries in the carjacking in Acocks Green, Birmingham.
Dozens of officers were deployed to search for the stolen grey Audi A3 S-line and it is believed the car was travelling towards Solihull, West Midlands, when it was last sighted.
The search for the vehicle is ongoing, with police tweeting: “Mum and baby will be re-united shortly, but we still have officers looking for a grey Audi A3 S line after the car-jacking in #AcocksGreen – have you seen it? Call 101″.
Police initially feared the baby would be abandoned by the carjackers, urging members of the public to keep an eye out for her.
Earlier, the force said: “Extensive police resources are looking for the car and are asking you for help – call us on 101.
“We believe they travelled towards Solihull. We would also ask you to look out for the child in case the offenders have realised what they have on board and abandoned her.
“Our priority is the baby’s safe return.”