The mum, who was 33 months pregnant, and felt poorly and short of breath, sat on a trolley at Hull Royal Infirmary for four hours before being discharged.
But she was in fact suffering from a rare and deadly build up of toxicity as her body was unable to process the prescription medicines, paracetamol and antibiotics, she had been taking, and her blood became dangerously acidic.
She collapsed on the way out and her baby daughter was delivered by emergency C-section, but died ten hours later.
The woman, now 29, who does not wish to be named, spent the next three weeks in a coma fighting for her life, not knowing the child had died.
Experts, who examined the case as part of a legal claim against the hospital trust, said the child could have survived if she had been delivered when she arrived in A&E.
The trust admitted mistakes and has paid Â£50,000 damages to the family after a claim of medical negligence was made via Hudgell Solicitors.
The mum, who has two children and has had two more with her partner since their daughter’s death in March 2014, said she was angry no one listened to her.
She said: The signs had been there with my two previous pregnancies, this had been happening for years, but with my daughter it became too much. I could have died too.
“I’d been feeling unwell for weeks, which is why I had been taking the medication. I was coughing and breathless, but no-one listened to me."
She passed out on her way out of the A& E department at 7.45am – four and a half hours after arriving at hospital.
She was taken to the Resuscitation Ward at 8.19am, and she was put to sleep for the delivery. At 9.33am her baby was delivered, but it was too late.
She said: "If any pregnant women feels something is wrong with her baby, I would now say go and get it checked out, and do not leave it until they can prove to you that there is nothing wrong. I had my instincts and I knew, but no-one took me seriously.”
Solicitor Nicola Evans, a specialist in handling cases of birth negligence at Hudgell Solicitors, said: “My client was dangerously ill when she was taken to Hull Royal Infirmary’s accident and emergency department and it is deeply worrying that, although a rare condition, it was not in the minds of doctors as a possibility.
“All too often we see cases where there are tragic circumstances as a result of thorough tests not being carried out on patients. Her treatment from walking in the door to walking out four hours later was shocking."
The trust carried out its own "Serious Untoward Incident" review following the baby's death, which identified a catalogue of errors, including human error on the part of the emergency doctor to recognise a sick patient and inappropriate discharge of a sick patient.
Mike Wright, chief nurse at Hull and East Yorkshire Hospitals NHS Trust, said: “We are very sorry for this family’s loss and would like to offer our condolences once again.
“This incident was thoroughly investigated by the Trust back in 2014 and various learning points, both for individuals and for the organisation, have since been identified and acted upon.
“We are, however, concerned to hear suggestions that this patient was made to feel uncomfortable or under suspicion of self-harming while in our care.
These are concerns which have not been raised with us previously and as such, we would encourage the patient to speak with our Patient Advice and Liaison Team in order that we can look into these further, should she so wish.”