Rebecca Wilson, 33, of Wenlock Road, South Shields, was with mum Susan when a man entered her house through the unlocked front door and took her car keys.
The mother-of-two disturbed the thief and challenged him in the front garden, not realising he had already taken her car keys.
As she checked to see what had been stolen, he drove off in her car.
The raid took place at about 1am on January 2, and the car was recovered later that morning.
She said: “When I went to the front door, it was open and a man was standing outside. When I asked him what he was doing, he said he was trying to get my dog back in the house from the garden.
“This conversation went on for a couple of minutes, because I didn’t believe him, and eventually he walked away and I went around the whole house to check nothing had been taken before locking all my doors.
“I went to put my shoes on to check the car and saw the brake lights were on. When I opened the front door and got outside, he drove off. I couldn’t believe it.”
She added: “All the lights were on in the house, so you wouldn’t expect anyone to even attempt it. The worst thing was that I could see him driving off in my car, yet couldn’t do anything about it.”
Miss Wilson’s partner, Ronald Coxon, was at work at the time, while her children Jacob – who is aged 33 weeks and was born 15 weeks prematurely – and six-year-old Jaden were also in the household.
The car is a lifeline for the family, with Jacob regularly needing to be taken to hospital check-ups in Newcastle.
They are now without the car, which is with an insurance company as it has its locks changed.
Miss Wilson added: “I’d urge anyone to always lock their doors, because I certainly do now.
“At the time, I just didn’t even think about it. I was in a rush to see my son, because he was poorly, so I just threw the keys on the stairs when I came running in.
“Now we still can’t use the car and that is really important because we’ve got hospital appointments nearly every day with the baby.
“I’ve now got to rely on other people to take me there.”
Police say a man was arrested over the incident, but released with no further action taken.
A Northumbria Police spokesman said: “Police are carrying out inquiries after a report of a burglary in Wenlock Road, South Shields, on Saturday, January 2.
“Burglars broke in and stole the car keys, and the car was subsequently stolen. The car was later recovered.
“Inquiries are ongoing. Anyone with information can contact Northumbria Police on 101, quoting reference 6802 0116, or Crimestoppers anonymously on 0800 555 111.”