Amy Wigfull, 25, suffered serious injuries after falling from a fifth-floor window three years ago.
She had metal screws inserted to hold her pelvis together and was told she would be unable to cope with the weight of a baby.
But Wigfull gave birth to Ralph last month and says being a mum is the best thing that's ever happened to her.
"Now Ralph is here I feel incredibly lucky," she said. "I'm alive, I've learned to walk again and now I'm a mum.
"Ralph is my little miracle. It seems too unbelievable."
Wigfull was on holiday celebrating her mum Shelly's 40th birthday when she suffered the fall.
While sleepwalking, she got out of bed, walked into the bathroom, climbed into the bath and opened the fifth floor window, before crawling out and falling onto the concrete below.
Doctors said had she fallen a few metres to the left she would have hit a motorbike, or a few metres to the right she would have hit some boulders.
After the fall, she was found almost immediately by a man who had gone for a walk.
Wigfull was immediately rushed to hospital to be treated. She suffered a broken wrist, shoulder and pelvis, a punctured lung, bleeding on the brain and broken vertebra in her back.
After a month in a Spanish hospital she returned home to Goldthorpe, South Yorkshire, and continued to get better.
As she learned to walk again, Wigfull, who has no recollection of the fall, was told that her body wouldn't be able to cope with pregnancy.
She said: "When the doctors said it was unlikely I'd be able to have children, I was heartbroken.
"I was so relieved to be alive, I tried to push it to the back of my mind but the worry never went away."
Wigfull - who never had a history of sleepwalking - believes her night-time wandering was caused by sunstroke.
"At first I thought I'd never walk again but I was so determined," she said. "Six weeks after the fall, I was taking a few steps.
"Then I broached the subject of babies again with my consultant. My periods were all over the place, which I blamed on the accident, and I wanted to know if my injuries would stop me from conceiving.
"Two metal rods were holding my pelvis together so the consultant said it was very unlikely that I'd be able to carry a baby.
"Even if I conceived there was a huge risk I'd have a miscarriage because there wasn't enough room in my pelvis for the baby to grow.
"Although having children wasn't on my list of priorities, I knew I wanted to be a mum someday, so to be told it might never happen was devastating."
Wigfull and her partner Andy struggled to come to terms with the news, but Wigfull focused on her recovery.
Last May she realised her period was late and recalled: "We hadn't bothered using contraception because I didn't think I could get pregnant, so I didn't see the point.
"After four pregnancy tests, the news started to sink in, but I was terrified I'd lose the baby. I was on edge until the moment Ralph arrived."
Wigfull was given regular scans to check the baby's growth.
"Seeing the heartbeat at my first scan was amazing and people were constantly commenting on the size of my bump so my instincts told me the baby was growing well," she said.
"I carried the baby high up, which is probably how it found the room to grow.
"When I was three months' pregnant I was told I wouldn't be able to have a natural birth because the baby wouldn't be able to pass through my pelvis, so a caesarean at 39 weeks was the only option.
"As I got bigger I started to get pain in my hip and back, but all I cared about was the baby and that it was healthy.
"My body had been through so much after the accident and I've still no idea how I managed to carry a baby to full term."
Ralph was born on 29 December weighing 6lb 13oz at Rotherham Hospital.