A 30-year-old Sydney mother has been charged with trying to kill her newborn son by abandoning him in a roadside drain for five days before passers-by heard his cries, police said Monday.

The week-old baby was in serious but stable condition in Westmead Children's Hospital a day after cyclists found him in a 8-foot deep drain beside the M7 Motorway in the suburb of Quakers Hill, police said in a statement.

His mother, Saifale Nai, did not appear in court to answer the attempted murder charge. Her lawyer did not enter a plea and the magistrate formally refused her bail.

Nai will remain in custody until her next court appearance on Friday. She would face a potential maximum sentence of 25 years in prison if convicted.

"Police will allege the baby, believed to have been born on Monday (Nov. 17), was placed into the drain on Tuesday," the police statement said.

Andrew Pesce, a gynecologist, obstetrician and former president of the Australian Medical Association, said such an ordeal could leave a newborn with long-term problems such as brain damage.

"There would still have to be some concerns about the baby," Pesce said.

"I would have thought that it wouldn't have been able to survive for much longer if it didn't start getting fed," he added.

He said healthy newborns have reserves to cope with relative malnutrition and often lose 10 percent of their birth weight because their mothers can take a few days before producing sufficient milk.

Helen Polley, a senator in the opposition Labor Party, said the near-tragedy could have been avoided if emergency hatches were rolled out at Australian hospitals, police and fire stations where babies could be safely abandoned.

She called for the repeal of laws that make child abandonment a criminal offense, which she said encourage the problem to be hidden.

Cyclists riding along a bicycle lane beside the motorway heard the baby on Sunday morning.

"We actually thought it was a kitten at first, but when we went down there we could hear exactly what it was — you could definitely tell it was a baby screaming," cyclist David Otte told The Daily Telegraph newspaper.

It took six men, including three police officers, to lift the 440-pound concrete lid that covered the drain, the newspaper said.

Police suspect the baby was squeezed through the drain's narrow opening and dropped to the bottom.

The baby was found wrapped in a hospital blanket, and police used hospital records to find the mother.

The baby would likely be taken into state care when he was discharged from the hospital, officials said.