Little Myla-Jai Sharon Thomas was diagnosed in the womb at 20 weeks with a congenital diaphragmatic hernia (CDH) - an extremely rare disorder affecting around one in 2,500 babies born in the UK.
She was born on July 27 and, despite the best efforts of medics at Sheffield's Jessop Wing, she sadly passed away three days later on July 30.
Her mother Demi Wragg, from Parson Cross, opened up about her and her partner Jack Thomas's heartache ahead of a charity fundraising event in Myla-Jai's memory.
She told how she had regular checks after the condition was detected, and Myla-Jai had been given an 80 per cent chance of survival.
But her daughter arrived after only 32 weeks, with one lung not working at all and the other only operating at less than half the expected capacity.
She was placed on a ventilator but after doing well for the first day-and-a-half, her blood pressure and oxygen levels began dropping and she eventually lost her fight for life.
"We only had a few days with Myla-Jai, but that time meant everything to us," said Demi, a 20-year-old support worker and hairdresser.
"We got to hold her and bathe her and dress her. We were able to say a proper goodbye to our precious girl, and we had castings made of her hands and feet."
Demi knew nothing about CDH before Myla-Jai was diagnosed, and when she told friends and family they were all equally in the dark about the condition.
She wants to increase awareness of the disorder and raise money to support for other families affected and fund more potentially life-saving research.
The Barrel pub on Lane End, in Chapeltown, is hosting a memorial fun day for Myla-Jai, in aid of the charity CDH UK, next Sunday, August 26.
The event, running from midday to 6pm, will include live music, face-painting, a bouncy castle and more.
Demi said: "It's very special to us to have this day in Myla-Jai's memory. Hopefully we will raise lots of money and help spread the word about CDH."
Her friend KelseÄ— Cocking, who has organised the event, said she wanted to do something special in Myla-Jai's memory.
"I'm doing this so we can all spend this extra day sending her off again in a beautiful way and so everyone can have a fun day on behalf of Demi's beautiful little girl," she added.
CDH occurs when an unborn baby's diaphragm fails to develop correctly, allowing the contents of its abdomen to protrude into the chest cavity, which in turn prevents the lungs from forming properly. There is currently no known cause or risk factor, according to CDH UK.
For more about the condition, visit: www.cdhuk.org.uk.