'Extremely Healthy' Baby Dies of Mysterious Sudden Infant Death Syndrome

A mother has shared her heartbreaking experience of losing a baby girl to Sudden Infant Death Syndrome (SIDS) in order to raise awareness about the mysterious condition.

Jasmyn Willcox was just five months and one week old when she died in her sleep during a winter's night in 2017. A coroner determined that the young child was "extremely healthy," and found "no reason for her death."

The mother Liz Willcox—from the Queensland state in northeastern Australia—told 7NEWS.com.au of her shock after finding her baby dead in the morning.

"I looked at the baby monitor and saw how still she was," Willcox told 7NEWS in a story published on Sunday. "I just started grabbing her and she was cold and lifeless."

"I alerted my husband Ben, we called an ambulance and he started performing CPR. But I just shut down."

Following the death of their daughter, Willcox and her partner learned about SIDS. The pair said they had vaguely heard about the syndrome.

"It just wasn't something we'd been privy to," Willcox told 7NEWS. "Because there just hadn't been a lot of attention on the topic."

SIDS refers to the unexplained death, usually during sleep, of a seemingly healthy baby that is less than one year of age, according to the Mayo Clinic.

Boston Children's Hospital says around 2,300 babies in the United States die of SIDS every year.

The cause of the mysterious syndrome is unknown, but it seems as if SIDS is associated with certain physical and environmental factors.

"No one can comprehend how a healthy baby put to sleep can be found dead the next morning," Rita Machaalani, a clinical associate professor at the University of Sydney, told 7NEWS.

"A 'stigma' usually surrounds the parent that they must have done something, but that's far from the truth."

One of the physical risk factors associated with SIDS has been defects in the part of an infant's brain that is responsible for breathing and arousal from sleep. Low birth weight and a recent respiratory infection have also been identified as physical risk factors, according to the Mayo Clinic.

Environmental factors can also combine with these physical ones to increase the risk of SIDS. These include sleeping on the stomach or side, sleeping on a soft surface and overheating.

Still according to the Mayo Clinic, SIDS is slightly more likely to affect boys than girls, and is more common in babies aged between one and 4 months old. The risk of SIDS also increases if the mother, when pregnant, is younger than 20, smokes cigarettes, or uses drugs or alcohol.

Only when all other causes have been excluded, can a diagnosis of SIDS be determined.