A post-mortem examination this morning of a newborn girl, whose body was dumped in a Lower Hutt back yard, is expected to shed light on the circumstances around her death.
The infant's body was found wrapped in a towel at a Taita Drive property on Monday morning, and her mother was located yesterday afternoon.
Inspector Shane Cotter said the woman in her early 20s was identified as the baby's mother after a search of the area yesterday.
The woman had not sought any medical attention, he said.
"However, she has since been hospitalised ... and is being treated for complications as a result of the birth.''
Police were continuing to investigate the circumstances of the baby's birth.
A post-mortem examination this morning would determine whether the infant was stillborn, as well as how old she was.
Mr Cotter said the baby appeared to be no more than a day old and still had part of her umbilical cord attached.
A police spokeswoman said it was too early to determine whether any charges would be laid against the mother.
The woman who found the body and her partner, both aged in their 60s, were surprised and distressed by the discovery, Mr Cotter said.
"I spoke to the man at the address and he said if it was alive they could have just left it on our front door step, rung the doorbell and run away and we would have looked after it. They didn't need the distress for what they found in their backyard.''
The pair were dealing with it "as best as they can'' and wanted to recognise what had happened in some way.
"Plant a tree there or something along those lines to acknowledge this wee baby's life.''
Taita Drive resident Maria Tagoai said yesterday her neighbour had been hanging out washing in the back garden when she made the discovery.
"She went outside to hang her washing and she saw a dead baby, a dead body of a newborn baby at her garden, and she collapsed.''
Mr Cotter worked on a similar case about five years ago in which a woman hid her pregnancy, and after a few days put the baby's body into a cardboard box in her backyard at a boarding house.
She pleaded guilty to infanticide.