A 19-year-old man was arrested at 4:30pm, two hours after the accident.
The mother and baby were taken to the Astrid Lingren Children’s Hospital in Stockholm, where they were both treated for minor injuries. The baby had minor lung injuries, and the mother was grazed on her face and legs.
The man is suspected of careless driving and causing actual bodily harm.
The police were alerted to the accident, on Sulvägen in Solberga, at 2:27pm. The car was found abandoned shortly after the accident on the crossing of Kristallvägen and Folkparksvägen. Police say the car had been bought by a relative of the man from a dealer in Södertälje on Thursday evening.