The fast-rising tot floored her shocked mum when she came along in the elevator at Norfolk and Norwich University Hospital.
Natalya emerged as mum Suzy Bunn, 29, was due to be induced because she was 11 days overdue.
Suzy, from Mattishall, Norfolk, said: 'We were walking across the hospital car park and I thought she was coming.
'We got in the lift to meet the midwife when I had another contraction.
'As the doors opened, a midwife and a nurse were waiting there with a wheelchair but as I moved to get in it, Natalya was born.
'The midwife managed to catch the baby just in time.'
Suzy was back home within six hours of giving birth and proudly showed off the new family member to seven-year-old daughter Alanna.
She said: ' Alanna is a very proud big sister and is telling everyone about her baby sister being born in a lift.
'When Natayla gets married it will definitely be something Jason mentions in the speech.'