Paramedics called by a woman pregnant with twins had to get the police to break down her door after she collapsed on the bathroom floor, their inquest was told.
Chantelle Page, 28, and her daughters did not survive the coronary thrombosis she suffered, said to be a rare complication of pregnancy.
Twins Violet Rose and Lilly Mae were delivered by Caesarian section at the Friarage Hospital, Northallerton, North Yorkshire, immediately upon their mother's arrival there on September 6.
Coroner Michael Oakley, sitting at County Hall, Northallerton, heard that Lilly Mae was stillborn and Violet Rose died around 30 minutes later, after only faint signs of life had been found.
The twins were delivered at around 27 weeks gestation, the inquest heard.
Ms Page, who was asthmatic and a smoker, rang twice for an ambulance after complaining of chest pains and difficulty breathing.
A first ambulance had been diverted away to a higher priority call for a patient who could not breathe, the hearing was told.
Clare Appleton, an emergency care assistant for the Yorkshire Ambulance Service, said a crew was sent to Ms Page's flat in Topcliffe, near Thirsk, and when there was no response, police were called to break down the door.
Ms Page had been alone in the flat and was found lying face down on the bathroom floor.
Attempts were made to revive her, including assistance from an air ambulance crew.
The customer care assistant was driven to the Friarage Hospital where an emergency care team was waiting when the ambulance arrived.
Mr Oakley recorded that the deaths of Ms Page and Violet Rose were from natural causes and Lilly Mae was stillborn.
He said: "These were very distressing occurrences, distressing not only to the family, likely they were distressing to the medical staff who attended them. I don't think there are any big lessons to be learned from this at all, it was one of those very tragic occurrences and my sympathies go to her family."
In a statement to the inquest, the twins' father Mark Bramhald said he had struggled to understand the tragedy and has needed hospital treatment.