When Jessica Stubbins went into labour in the early hours of Sunday morning, she told husband Tom to drop her at the hospital entrance before finding a parking spot.
But by the time the dad arrived back by his wife's side, baby Lucy had been born and was being cradled in her mother's arms.
Amazing CCTV footage shows Jessica delivering the baby on her own while standing up in the doorway of UK's Scunthorpe Hospital within a minute of getting out of the car.
"I just told Tom he best drop me off at the door as he parked the car," the UK mum told Good Morning Britain.
"And then I was trying to close the door really quick and then as I got out I just knew that she was on the way."
When her husband arrived back by his wife's side Jessica said: "It's a girl, it's a girl! I'm sorry, I'm sorry!"
"She felt really guilty because I missed it," Tom told GMB. "I was just in absolute shock and I didn't know what was happening.
"It was only about a hundred feet away and I still missed it."
Jessica had been to the hospital earlier in the day as she thought labour may have started, but ended up going home believing it was a false alarm.
After having a warm bath in the evening contractions started again, and Jessica realised the baby was on its way.
Midwife Sally Parkin was one of the first people on the scene after the doorway birth of little Lucy.
"We met a burly security guard with a huge smile on his face and the whole environment was very calm," she told GMB.
"Jessica was just so calm and relaxed, and Tom was crying and Jessica was saying, 'I'm sorry, I'm sorry' while he was telling her it didn't matter.
"It was just a lovely experience, she did so well."