SINGAPORE - There are three possible reasons behind the death of a six-month-old boy who was found face down in a flat while under the care of a nanny.

Dr Audrey Yeo, a forensic pathologist from the Health Sciences Authority, said this on Monday as she testified on the first day of a coroner’s inquiry into the death of Yong Jing Yu.

The infant had been under the care of the nanny since he was around three months old.

On Dec 28, 2021, the day of his death, the nanny fed him milk and put him to bed in a playpen at around 3pm, said investigation officer (IO) Russel Tong on Monday.

When the nanny found him in a prone position with his face down around 6.20pm and saw that his face had turned blue, she called for an ambulance.

IO Tong, who is a senior staff sergeant at Ang Mo Kio Police Division, said the Singapore Civil Defence Force gave the nanny instructions to try to resuscitate the baby.

Paramedics took over resuscitation efforts when they arrived, and the baby was taken to Sengkang General Hospital, where he was pronounced dead.

The police do not suspect foul play, said IO Tong.

Dr Yeo provided the final cause of death to be unascertained, as there are three possible causes that could have led to Jing Yu’s death.

She testified that the first is positional asphyxia as the baby was found face down.

In highlighting the second possible cause, she said she also found some acute inflammation in Jing Yu’s lungs. But as the inflammation was not extensive enough to point to pneumonia, this finding is insufficient to be labelled as the final cause of death.

The third possible reason, Dr Yeo said, is a gene mutation. During the autopsy, she found a gene mutation which affects the transportation of ions to the heart.

“Any mutations to this gene could cause abnormal heart rhythms. If the heart cannot beat regularly, it may not be able to sustain life. But it is not known whether this caused the death of Jing Yu,” she said.

Dr Yeo noted that while these three points are possible causes of death, she is unable to rule one cause to be more likely than the other.

On Monday, IO Tong said the nanny had left her Sengkang flat when Jing Yu was asleep. It was not mentioned why and for how long she was gone.

Addressing IO Tong, Jing Yu’s parents, Mr Yong Chen Seng and Madam Toh Jinq Lay, who spoke in court with the help of a Mandarin interpreter, asked who was looking after their son when the nanny was out.

He said the nanny’s 13-year-old son was the only person at home at the time, “so she assumed her son would be the one taking care” of the baby.

In addition to Jing Yu, the nanny was also babysitting two other babies at the time.

When State Coroner Adam Nakhoda asked if there was evidence the nanny’s son left his room to check on Jing Yu and the other two babies, IO Tong said “no”.

Madam Toh said the nanny she hired had “a habit” of wrapping Jing Yu and letting him sleep face down, and asked IO Tong if the nanny had let her baby sleep in that position on the day he died.

IO Tong said he was unable to state what position the nanny had let Jing Yu sleep in but confirmed he was found face down.

The state coroner will give his findings at a later date.