The mother of four, aged 42, decided to undergo a sterilisation after she and her husband David, 52, felt that they could not afford a bigger family.
But at Christmas she started to feel sick and later discovered she was pregnant with little Layla, who arrived a week before she was due to be delivered by caesarean section.
Mrs Davies of Hawshaw Lane, Hoyland, Barnsley, said: “I was devastated at first. It took quite a few weeks to come round to the idea. I kept asking how could it have happened?”
But she said she is now overjoyed at being a mother again despite the problem of finding space for the new addition in the family’s three-bedroom semi-detached house.
Although eldest daughter Tasha, 20, has moved out she still has Hayley, 14, Lloyd, eight, and Libby, three at home.
When Mrs Davies returns to work, her husband is giving up his job as a self-employed car salesman because the family cannot afford childcare.
He is also having an operation to make certain that Layla has no more siblings.