SINGAPORE - A 25-year-old woman pleaded guilty on Monday (Sept 26) to two charges of letting her boyfriend abuse her then one-year-old son, who suffered a broken skull after being pushed off a bed by him on one occasion.

The infant had bleeding in his brain, but survived the ordeal on March 25 last year - after emergency surgery. Now aged three, the boy is in foster care and undergoing rehabilitative therapy. The mother has weekly access to him.

The prosecution is seeking one year's jail for the woman, a part-time sales assistant, who cannot be named to protect the identity of her child.

She will be sentenced at a later date. Defence lawyer A. Revi Shanker will argue for a more lenient sentence before District Judge Adam Nakhoda on Oct 27.

The tormentor, Franklie Tan Guang Wei, 26, was sentenced last Monday (Sept 19) to 6 ½ years' jail and six strokes of the cane. He had pleaded guilty to one charge of causing grievous hurt and three out of four charges of ill-treating a child.

Assistant Public Prosecutor (APP) Dillon Kok said the mother had displayed "an utter disregard for the victim's well-being" and repeatedly turned a blind eye to Tan's abuses.

"In committing these offences against her own child, (the mother) had breached the fundamental trust that exists between a parent and child," he said.

"Her dereliction of duty as a mother ... can only be described as being persistently delinquent."

APP Kok added: "Perhaps misguided by her love for Franklie, the accused selfishly chose her relationship over the well-being of her own child, exposing him to the horrors of abuse resulting in tragic consequences.

"Her act of condoning such abuse to the extent of persistently placing the victim within the grasp of his tormentor is particularly reprehensible."

The boy was born in mid-2013, after his father lost contact with his mother. In August 2014, she got into a relationship with Tan, who did odd jobs and last worked at a mobile phone shop. The following month, the infant's behaviour changed.

"(He) appeared to be fearful of males and started having nightmares in his sleep," APP Kok said.

Two nannies who looked after him also found bruises on his body.

"When (the mother) was questioned, she denied that (he) had been abused and claimed that there were 'spirits' in the flat," APP Kok added.

In November 2014, the mother got pregnant with Tan's child and moved in with Tan and his mother.

On Nov 8, the baby's cries woke the couple. Tan slapped him once, leaving finger marks on his cheek and bruising near his ear.

Three days after the incident, a nanny took photos of the bruises and swelling. She made a police report about the injuries on Nov 19 and the Child Protective Service was informed. The baby was then put under the nannies' care, and the mother and Tan were allowed only weekly supervised access. Tan's grandparents later took over from the nannies in taking care of the baby in February last year, with the couple granted supervised access again.

But on March 8 last year, Tan's grandfather left the infant at Tan's flat. That night, frustrated with his cries, Tan threw the baby at his mother, who was about 2m away. The infant fell against her body.

Later, Tan and the mother were allowed to spend the nights with him. But on the morning of March 25, angered by the baby's cries, Tan hit his buttocks twice, causing a bruise.

After the mother went to work, leaving the infant alone with Tan, the baby vomited on the bed. Angry, Tan forcefully pushed him off the bed with his right arm.

The infant landed face-up on the floor about 2m away and vomited. Tan took him to the toilet to shower but did not check the water temperature first, scalding his upper back.

Later, Tan noticed that the baby was in a daze and semi-conscious. He was also vomiting repeatedly. Tan told the mother, who went home to find the infant weak and very pale. They then took him to hospital.

Tan has started serving his sentence, although he has also filed an appeal against the sentence. The boy he fathered with the accused is currently one-year-old and in her care.

The maximum punishment for permitting a child to be ill-treated, under the Children and Young Persons Act, is a $4,000 fine and four years' jail.