The 6lb 14oz infant was found with her umbilical cord intact, next to a house in Wansford Way, Whickham, Gates-head, by Darren Simms, 13, as he cycled home from his morning paper round on Thursday.
The baby, named Molly by staff at Queen Elizabeth Hospital, Tyne and Wear, is said to be making satisfactory progress.
Police said they wanted to trace the mother because they believe she needs medical attention.
The teenage mother of another newborn baby found abandoned and blue with cold in a park two days before Christmas has come forward, Essex police said yesterday.
A 15-year-old girl and a female companion visited Ilford police station, late last night following four days of appeals by Scotland Yard.
The baby boy, named Joseph by nurses at Harold Wood Hospital, in Essex, where he was being treated, was discovered by a street cleaner in Goodmayes Park in Ilford. The child, who weighed six-and-a-half pounds, was suffering from hypothermia. Doctors believe he had been born less than an hour earlier.
Joseph is now in an incubator, being watched by a team of nurses in the Harold Wood maternity ward, where his condition is described as stable.
A Scotland Yard spokesman yesterday said: "It is too early to say whether Joseph will be going back with his mother. That is a decision for the social services and not the police."Reuse content