Doctors were unable to explain how a new born baby died after her horrified parents awoke to find her not breathing.
Little Evie McElhinney, five weeks old, had been taken to sleep in her parent's bed after waking up crying in the night, an inquest at St Helens Town Hall heard.
But when her dad went to wake her on the morning of January 29 last year, he could not rouse her and noticed a small amount of blood coming from her mouth.
Paramedics rushed to the house in Kipling Avenue, Huyton , but could not save Evie.
Giving evidence during the inquest, clerk Gavin Farrell told the court: "Evie had no health issues following her birth.
"On the night of Sunday January 28 Evie was taken to bed by her dad. Initially she had been placed in a Moses basket, but during the course of the night she cried and was taken to her parent's bed.
"At around 7am her dad awoke and found Evie unresponsive with blood coming from her mouth."
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Mr Farrell said Merseyside Police conducted an investigation but there was no sign of trauma or violence to Evie, the house was clean and tidy and stocked with food and her mum and dad tested negative for any drugs or alcohol.
The court heard the couple indicated co-sleeping with Evie was a common occurence.
A post-mortem exam found no signs of injury and a medical cause of death could not be ascertained despite toxicology and haematology tests.
Mr Farrell said medical experts indicated there had been cases where babies with undiagnosed heart conditions have died suddenly while co-sleeping in the past.
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However doctors could not agree what caused Evie's death.
Johanna Thompson, assistant coroner for Sefton, Knowsley and St Helens, recorded an open verdict.
