She was bailed to a Kaitaia address, despite police opposition, but is to reappear in court on Wednesday.
Detective Senior Sergeant Mark Loper said as the matter was before the court he could not reveal what injuries the baby had suffered.
He also could not detail what the circumstances were surrounding the infant's death but said the family was not known to police and did not have a history of domestic violence.
Asked if the charge could be upgraded to homicide, Mr Loper said: "It's too early to say yet".
"Why I say that is the autopsy at the weekend was inconclusive and we are waiting for forensics so until we get a definite cause of death we wont be able to proceed."
"At this stage we can't say that this is a death as a result of child abuse," he said.
Mr Loper said forensic scene examination results could take up to six weeks.
The house where the baby was found was empty when the Herald visited earlier today.
Neighbours said the man and the woman at the address were generally polite and quiet.
"There was the odd party but we are probably noisier than they are," said one woman who only wanted to be known as "Sandra".
Police said the baby's body was released yesterday following an inconclusive post mortem.
He has been taken to Kaitaia where he will be buried.
