A 19-day-old baby boy suffocated while lying on the bed with his father, who was sleeping.

A pillow was later found over the infant's upper body.

It was the first time the baby had been put on the bed next to one of his sleeping parents, and his mother placed him there as she did not want him to be alone while she gave an older child a bath.

She gave the baby's father a tap on his body and told him to watch out for the infant. But the father said he was too tired and was not aware that his wife had alerted him.

Less than two hours after she had left the infant on the bed, the mother returned to find the pillow over the baby, who was sent to the hospital where he was pronounced dead at 2.26am on June 10 last year.

State Coroner Kamala Ponnampalam ruled the death of Muhammad Umair Muhammad Raihan an "unfortunate misadventure".

"This case is yet another unfortunate illustration of the increased risk of inadvertent suffocation resulting from co-sleeping with one's infant, for however brief a time," the coroner said after the inquiry last month.

The coroner had ruled on two other accidental infant deaths in the same month.

In one case, the death of 15-day-old Nor Eilshan Emran Muhammad Nor Aszroy was likely to have been due to "unintentional suffocation", the coroner said, after his mother dozed off while breastfeeding him.

In the other case, seven-month-old Yuri Chua Le En suffocated after being trapped between her mattress and a padded bed rail.

In her findings for the latest case, released yesterday, the coroner said parents must be vigilant and observe safe sleeping habits at all times.

The coroner heard that Muhammad Umair's father worked throughout the night of June 8 last year, and went to sleep in the master bedroom at 6.30am the next day.

At about 7am, the baby's mother placed her son next to his sleeping father because she did not want to leave the infant alone as he was prone to spitting or vomiting after being fed. The mother also thought it prudent to do so as she was going to be away from the room while bathing her other child.

But at about 8.45am, the mother returned and found a pillow over Muhammad Umair.

The father started performing cardiopulmonary resuscitation when he realised his son was not breathing.

Muhammad Umair was taken to Changi General Hospital, and then transferred to KK Women's and Children's Hospital, but his condition continued to deteriorate. He was subsequently pronounced dead, despite "maximal medical management".