The actress plays Maxine Minniver in the Channel 4 soap, who went into labour after being driven off the road by villainous husband Patrick Blake (Jeremy Sheffield), who then delivered the baby!
She told What's on TV: "The whole birthing thing was a lot of fun to do because I've never given birth... so it was something a bit different and fun and it wasn't in a clean hospital, it was in a dirty shack."
Nikki added: "[I had no] coaching. I spoke to a lot of people who've had children and the main point was you're in a lot of pain so that's what I've tried to do, to be in a lot of pain...
"Jeremy was wonderful. He did think my face was very funny, but to give him credit I do look hilarious, so I don't mind people laughing at me a bit."
Co-star Danny Mac interjected: "I really wanted him to say, 'Don't worry I've been in Holby! I've played a doctor, you'll be fine!'"
Jeremy starred in Holby City for three years in the early 2000s.
Watch the interview about the Hollyoaks train crash and birth with Nikki Sanderson and Danny Mac, above.
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Patrick McLennan is a London-based journalist and documentary maker who has worked as a writer, sub-editor, digital editor and TV producer in the UK and New Zealand. His CV includes spells as a news producer at the BBC and TVNZ, as well as web editor for Time Inc UK. He has produced TV news and entertainment features on personalities as diverse as Nick Cave, Tom Hardy, Clive James, Jodie Marsh and Kevin Bacon and he co-produced and directed The Ponds, which has screened in UK cinemas, BBC Four and is currently available on Netflix.
An entertainment writer with a diverse taste in TV and film, he lists Seinfeld, The Sopranos, The Chase, The Thick of It and Detectorists among his favourite shows, but steers well clear of most sci-fi.