A missing mother who might have given birth next to a Sydney river delivered a baby boy, forensic tests have revealed.
Investigators are yet to track down the woman or the child nearly three days after a dog walker discovered a placenta and umbilical cord on the banks of the Cooks River at Earlwood.
Testing of the material revealed the placenta and cord belonged to a baby boy, police said on Thursday.
Authorities have feared for the safety of both the mother and child since the material was found on Monday afternoon by the suburban riverside, which is about 10km southwest of the city centre.
The mother is still being urged to seek medical attention and attend a nearby hospital as police insist the health of her and her son remains their top priority.
A full-scale search of the area on Tuesday did not show any evidence the baby had been harmed, nor did it reveal any immediate clues to why the placenta and umbilical cord had been left there.
Police divers and a blood detection dog were called in before the search wrapped up later that afternoon.
The Cooks River flows from Yagoona in Sydney's outer southwest and runs into Botany Bay at Kyeemagh, 23km away.
Sections are heavily polluted as a result of traffic congestion, litter, sewage, illegal dumping and industrial and domestic activities.
