When baby Harry Downes died aged just one day, his parents were shocked to discover he had a heart murmur.
They could not believe a baby could develop such a condition.
As they grieved, Harry's mother Lisa and husband David began to wonder how many other parents had suffered such a tragedy.
They wanted to let more people know that children were at risk from health problems and decided to set up a charity to raise money for other sick children.
The Baby Harry Memorial Fund, which opened in October, has so far raised more than £7,000 for the Royal Sussex County Hospital in Brighton and Guy's Hospital in London, where Harry was treated.
Harry was born at 10.30am on October 5 last year at the Royal Sussex, weighing 7lb 10oz.
When doctors examined him they found he had a heart murmur.
He was treated at the Trevor Mann baby unit and later that evening transferred to Guy's.
Specialists discovered the murmur was caused by too much blood passing through his heart, which had made one side enlarge.
Despite the efforts of a team of medics, Harry died at Guy's at 8.30pm the next day.
Mrs Downes said: "I was completely oblivious to the fact something like this could happen.
"I just took it for granted my baby would be healthy.
"There was nothing wrong in my pregnancy. It was only eight hours after Harry was born that we realised something was wrong.
"We decided to set up the fund to keep Harry's memory alive and help other families."
Mrs Downes, 33, from Lower Bevendean Avenue, Brighton, said staff at the two hospitals were incredible and she wanted to give them as much help as possible to treat babies such as Harry.
The fund was a way of giving the doctors and nurses something back for their care and dedication.
Mrs Downes, who works for BT and Mr Downes, a locksmith and safe engineer, hope the money will buy equipment for the hospitals.
The equipment used to help keep babies like Harry alive includes drip pumps for intravenous lines, ventilators and breathing monitors, heart rate and oxygen level meters and X-ray, ultrasound and CT scanners.
Mrs Downes said: "We are under no illusions. We realise these things cost a lot of money but it's still our aim to contribute, even if it takes years and years.
"We haven't set a target, we just hope to keep raising money for as long as possible."
Mrs Downes, who has a ten-year-old son, Josh, from a previous marriage, said they had had tremendous support from local people.
She said: "Ryan Gayler, a friend of ours, is running a marathon in Switzerland in September and my husband is hoping to do the Great North Run."
David Rose Sports Club is sponsoring a paintball challenge at Holmbush Paintball, Faygate, near Horsham, on September 22.
The cost is £20 per player, £2.50 of which will go to the fund.
Holmbush Paintball will donate £1 from every 100 paintballs sold.
For more details, visit www.babyharry.org.uk or call David Rose Sports on 01273 326362
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