A woman is facing 25 years in jail for attempted murder after telling police she dumped her newborn baby in a stormwater drain, knowing it may kill him.

The 30-year-old woman did not appear at a brief hearing at Blacktown Local Court on Monday and remains in custody before her case is due to be heard again in Penrith on Friday.

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“The accused makes full admissions to putting the baby down the drain knowing it may kill the baby,” court documents said.

The court heard the boy was born in the early hours of Tuesday before being put through a drain’s narrow opening at Quakers Hill and dropped about 2.4 metres.

He was found five days later by a passing cyclist.

The mother lives at Quakers Hill, in Sydney’s west, with relatives but her parents are in Samoa.

A group of people who are believed to be her family members attended court on Monday but did not talk to reporters as they left.

The baby is now in a stable condition at Westmead children’s hospital and in the care of NSW Family and Community Services.

The baby was discovered, wrapped in a striped hospital blanket, down the drain on the side of a bike track along the M7 motorway just after 7.30am on Sunday.

Police doubt he would have survived Sunday’s 40-degree heat.

“It was already undernourished, and dehydration would have taken effect, so we would have had grave fears for the child’s welfare had it been exposed to this weather for the rest of the day,” Inspector David Lagats said.

Cyclist David Otte, out riding with his daughter, said he was meant to find the little boy.

“We’re not heroes or anything. We would have done it for anybody but we were just glad that we were there,” Mr Otte told Fairfax Radio.

Sydney obstetrician and gynaecologist Dr Andrew Pesce says newborn babies can survive for days without food.

“If it had been a really sickly child at birth, it probably wouldn’t have been able to survive,” the former Australian Medical Association president said.

“If it has underlying good health, they’re evolved to be able to withstand malnutrition in the first few days.”

“It’s quite normal for a baby to lose up to 10 per cent of its birth weight in the first few days after birth.”

-AAP