Selwa Romedan, 21, was found to have a narrowing of a valve in her heart after she collapsed and died in September 2016 following the birth of her daughter Sadenselwa.
In the days before her death, she suffered chest pains and shortness of breath and was told by staff at St James's Hospital, in Leeds, that she was anaemic and tired and was given a blood transfusion and told to rest.
Leeds Teaching Hospitals NHS Trust has now apologised to Miss Romedan's family and said an investigation found the young mother may have survived if her mitral valve stenosis condition had been diagnosed and treated.
Dr Yvette Oade, acting chief executive at the Trust, said: "Miss Romedan died in tragic circumstances in 2016 due to complications from an undiagnosed serious heart condition that remained asymptomatic during her pregnancy and subsequent delivery.
"At the time, we undertook a serious incident investigation to help us understand the cause and identify learning from this.
"This concluded that, if the condition had been diagnosed earlier, then treatment would have been provided for this.
"Had this procedure been performed then Miss Romedan may have survived.
"We understand the deep pain caused to Miss Romedan's partner and family and reiterate our sincere apologies and condolences for their loss."Muhanad Adem with his daughter Sadenselwa. Muhanad's partner Selwa Romedan, 21, died from an undiagnosed heart condition four days after giving birth. A hospital has said she could have been saved if her condition had been spotted and treated earlier (Image: Family handout/PA Wire)
Miss Romedan's partner, Muhanad Adem, described his pain at knowing the mother of his child could have survived.
He said: "It makes it worse knowing that they could have done something to save her. We came here to be safe and I put my trust in them."
The couple, who fled from Eritrea, north Africa, settled in Leeds after being granted asylum in the UK.
Mr Adem, 29, said his daughter's birth was the happiest day of their lives.
He said: "I cried with happiness when Saden was born and she was put in my arms."
But less than a day after being sent home, Miss Romedan was taken back to St James's Hospital by ambulance suffering shortness of breath and was diagnosed with anaemia and given a blood transfusion.
She was discharged the following day but her symptoms returned and the hospital's maternity assessment unit advised that she was probably just tired and told her to rest.
She collapsed in the early hours of September 25, 2016, after getting up to feed her daughter and telling Mr Adem she could not breathe.
Mr Adem said: "She said 'I am dying, I am going from you'. And she just collapsed - she fell down and I fell down with her."
The forklift truck driver was later told Miss Romedan had died.St. James's University Hospital
He said: "I didn't want to believe it at first and I didn't, not until I saw her. I kissed her and told her I loved her and I promised to look after the daughter she had given to me".
Mr Adem now devotes his life to looking after his daughter.
He said: "I know I have to live my life for my daughter. Saden is two and a half now and a strong, happy girl just like her mother. I have to be mum, dad, everything to her and give her all the chances we didn't get.
"It's very difficult though. I have no family around me. I have had to take time off work to care for her.
"I have a beautiful relationship with my daughter and I am so thankful for that, but I never imagined life would be like this".