The 38-year-old’s partner Joanne Mas had to have an emergency caesarean for the birth of their third child in 2013, due to complications.
Writing in his book Life Lessons from the East End, Danny said: “This was the first kid I’d had that I thought, ‘This could go wrong’.
“Childbirth is a worrying thing even if it’s all going well. Watching your missus go through it for six or seven hours isn’t easy.”
Danny added: “You’re watching the woman you love going through so much pain – and what can you say? Nothing. It’s an out-of-body experience.”
Danny – who also shares daughters Danni and Sunnie with Jo – revealed he thinks his EastEnders character Mick Carter could’ve handled the situation.
He continued: “You have to hold her hands and say the right things. I wish I’d played Mick Carter back then because he was like the perfect birthing partner.
“I could’ve nicked some lines, not in a cynical way but just to have something to comfort her. With Arty I really thought, ‘This kid could die’. He was premature – he came out weighing four pounds something, he was tiny.”
Arty was born just two days before Danny’s debut on the BBC One soap, meaning he failed to bond with his newborn.
“I had to cement my place in that show really quickly, otherwise it would have been a car crash and I wouldn’t have lasted,” Danny explained.
“I was getting home in time to put a bottle in his mouth just before he went to bed. That first year was tough. He wouldn’t come to me, he didn’t know who I was. That kills you.”