Clair Sudron, 32, was diagnosed with breast cancer two years ago and had surgery to remove a lump, while chemotherapy killed any remaining cancerous cells.
She had prepared herself for a life without children after doctors had warned her that, after four courses of the treatment, she would probably be left infertile.
But a year later, she discovered she was pregnant - and she gave birth to daughters Bella and Scarlett Herring seven weeks ago.
Clair, who lives with partner Steven Herring in Hartlepool, told her local paper: "I had all of the symptoms of being pregnant but to be honest I thought it was the chemotherapy, it really messes all of your systems up.
"But I did a few tests and they were all positive.
"I remember ringing my family and telling them I was going round to speak to them, they all thought I was going to tell them the cancer had came back.
"I had always wanted to have kids but I just figured I was going to have to have get used to the idea of not being able to.
"To find out I was pregnant and then to find out I was going to have twins was fantastic, absolutely fantastic."
Suggested For You
Get top stories and blog posts emailed to me each day. Newsletters may offer personalized content or advertisements. Learn more