Mark Critchard's endurance challenge is the last in a series of events that have been inspired by those affected by the death of a baby.
"Training's been tough - I'm just going to take it as it comes on the day, slowly, grit my teeth and get to the finish line."
Stillbirth and neonatal death are not rare events. In 2014, around 5600 babies died just before, during or soon after birth. That's over 100 babies every week.
It's a tragedy that can happen to anyone and at any time. It's devastating not just for parents, but also for friends and family.
Tina Clarke was one of seven who recently took on the 100km in the London 2 Brighton Challenge.
She ran for the Sands
charity because it supported her sister and brother-in-law when they lost their baby
James at 18 weeks.
Tina has also done some back to back marathons in the run up to this, one of which with children from Fishergate Primary where she Head Teacher, joined her for a mile each.
"The fact that I was raising money for a charity that helps parents to keep going kept me going!" says Tina.
Kristie Peach and her husband Chris took part for their son Joshua who was still born at 41 weeks 9th Oct 2012.
Alexandra Tuesley took part with the support of her sister Maxine Wilson and brother-in-law Steve.
This was in memory of her Alexandra's baby son Ben, one of her triplets who was stillborn on 21 June 2002.