For a dad, there is no experience on the planet that makes us feel as helpless as seeing our partner in labour. Will she be alright? Will the baby be alright? What can I do to make things easier?
It's a rollercoaster ride of emotions – but for new dad David Arshadi, it was 10 times that experience.
For when his wife Amanda went into labour at 28 weeks, the memories of what happened when he was a little boy came flooding back. When he was four years told, David's little sister was born prematurely. And tragically, she didn't survive.
That heartbreaking experience came flooding back to him when, 14 months ago, his baby daughter was born too early.
For several anxious days and nights, he waited and watched helplessly as Amanda became at the mercy of doctors as they tried to prevent her having an early birth. And in his darkest moments, he visualised the worst case scenario – as if preparing himself for tragedy.
But thankfully, when Leila was born, even though she was tiny, she was healthy. And although she stayed in hospital for six weeks, the 'little fighter' came through her struggles and is now a happy, thriving toddler.
During those terrifying times, David and Amanda needed the support of the premature baby charity Bliss. It is support that David hasn't forgotten.
Now he is determined to pay it back – by walking 630 miles around part of Britain's coastline. He and his friend Craig – who call themselves 2FatLads – are trekking the South West Coastal Path to raise money and awareness for Bliss.
As they trudged into the second week, I tracked them down to a cliff somewhere near Newquay in Cornwall to find out how the walk was going – and the story behind the lads' motivation in the first place.
Recalling the day his wife went into hospital at 28 weeks, David said: "Amanda is a midwife so she had felt that something was not quite right one morning - there had been a little but of 'show' and she knew that this was not normal that early on in the pregnancy.
"Luckily we lived about five minutes walk from the hospital where she worked, so she went over and was examined.
"She was told that labour could happen at any time so stayed in hospital for two nights and was given steroid injections to help the baby's lungs if Amanda was to go into labour.
"After the short spell in hospital, things seemed to calm down bit and we were told we could go home but Amanda was on strict bed rest to try and keep the baby in the womb for as long as possible.
"A week later we were having some dinner and Amanda went quiet for a while, I asked her what was wrong and she said in a very scared voice 'I think it's happening'.
"She'd been having early contractions and had been quietly counting the intervals, trying not to alarm me, but she obviously got to a point when, as a midwife, she knew that this time it really was happening. So off we went to the hospital.
"At this time I have to admit I have never been so worried in my life.
"I had no idea what to expect and the only experience I knew of about premature babies was my sister who was born 25 years ago when I was four, who died. Clearly this was running through my head during the whole ordeal.
"It sounds weird, but in a personal crisis, I tend to think of the worst case scenario, maybe as a way of preparing myself if the worst we're to happen.
"I began to think what would happen if we lost the baby, or if I lost both Amanda and the baby. At the time, despite the low risk of anything terrible happening to Amanda, it doesn't stop you from being absolutely terrified.
"The labour didn't last long as obviously the baby was so small. I remember the wave of relief that flooded over Amanda and me as our little girl Leila came out screaming - her lungs worked for sure!
"We were able to have a very quick cuddle before she was whisked away by an amazing team of doctors and nurses from the intensive care unit.
"Leila was in hospital for six weeks and proved to be a real fighter. She didn't ever require oxygen to help her breath, which is amazing, and apart from a few pretty dodgy days she was OK.
"As Amanda was an experienced midwife she was a lot more at ease and confident with Leila than me.
"I remember being nervous every morning that I arrived at the hospital, that long process of getting through into the ward, washing your hands, feels like it takes forever.
"All you want to do is rush in to see how your little girl is doing and whether she had a good night or whether she had taken a turn for the worse.
"I also became absolutely obsessed with the beeping monitors that Leila was attached to - if her sats dropped below a certain number or if her heart rate went up or down too much I would panic unnecessarily. As irrational as all my fears seem now, at the time it all feels so real.
"In the first few weeks of having Leila at home, it felt really strange because she was still like a tiny little doll, we kept of thinking 'are we sure she should be home with us?'
"Of course the doctors know exactly what they are doing and it was perfectly fine but certainly for the first couple of months we were probably a bit over protective of her as she seemed so delicate.
"Since then she's grown up into a beautiful little 14-month-old and although she is behind developmentally with a few things like walking we're not worried as we're just so proud of our little feisty girl."
TV editor David, 29, from Petersfield, Hants., added: "During the whole ordeal Bliss were a charity that gave a lot of comfort to us, not just in actual support but also the research and information that Amanda was able to utilise from them was amazing.
"They are a charity that truly do make such an impact on the families of premature babies. I decided that I wanted to give back to them so that other families could continue to benefit the way we did.
"I wanted to do something that seemed almost impossible for a person like me (not particularly fit) and this 630 mile walk around the South West Coastal Path seemed like a good challenge.
David had known his fellow Fat Lad Craig, 29 and single, from Mansfield, for nine years after meeting at university.
"I asked him to join me on the walk as I knew he was a stubborn bugger who would not give up under any circumstances and I knew that I needed someone like that to get me through the roughest and toughest parts of the walk," David added.
And there have been some very tough parts indeed. The walk is an official national trail called the South West Coastal path that is 630 miles long. It starts in Minehead in Somerset and goes all the way around the entire Devon and Cornish coasts to end up in Poole in Dorset. It's apparently the equivalent of going up and down Mount Everest four times due to the high cliffs and steep valleys.
But despite the literally blistering challenge and the pain of missing Amanda and Leila, David knows it will all be worthwhile in the end.
"We want to raise £10,000 for Bliss, and also by having a fairly big social media following increase the awareness for the charity and the needs of parents," he said.
"It's one of those things you don't think about until it happens to you.
"This is the longest I've ever been away from either Amanda or Leila and I am finding it really difficult.
"I've had a few moments of walking along quietly having a few tears, but luckily I can blame the wind if Craig sees me.
"But I know it will all be worthwhile in the end."
• To follow David and Craig, check out their blog and video diary at http://2fatlads.blogspot.co.uk/
• For more information about Bliss, go to http://www.bliss.org.uk/