Leanne Parrett, a paranormal investigator who lives near Bristol, went into labour on the day she was due to be induced.
After her waters broke on Thursday 11 October her husband Sam decided to drive her to Gloucestershire Royal Hospital in Gloucester.
On their way to the hospital, Leanne, who was 11 days overdue, felt the urge to push as they were about to join the M5.
Sam pulled into a lay-by and dialled 999 - but seconds later he was delivering his own son in the back seat on their car.
Ten minutes after giving birth to a baby boy with the help of the 999 operator, a paramedic arrived to help.
Leanne, 31, grabbed a quick selfie with the paramedic she described as 'amazing'.
Leanne said: 'We were so lucky there were no complications as it was just us.'