But the secretary from Warrington was shocked to find what she thought was a baby bump was actually a cancerous growth covering an area from her breast to her lower abdomen.
Kayleigh was diagnosed with Ewing's Sarcoma and had emergency chemotherapy to shrink the tumour. She lost her hair and eye-lashes during the treatment, but is now celebrating the all clear two years after her 'pregnancy belly' first started growing.
"I thought I was going to be a mother and I never thought for one moment I had a tumour growing inside me," Kayleigh said.
It just looked for all intents and purposes like a baby bump. I just couldn't believe it when I found out what it was.
"I'm just so relieved to be alive and hopefully I will have children in the future. I'm so excited for everything now. I can't wait to see what 2012 brings."
Before her diagnosis, Kayleigh suffered severe stomach pains, fatigue, loss of appetite and a rapidly growing stomach:
"I'd been to the doctors and they said it was something to do with my bowels. Pregnancy entered my mind as I had a boyfriend, but I was on the pill, and as soon as my tummy started to grow I did a test but it was negative."
After blood tests and an ultrasound, Kayleigh was shocked to be told she actually had cancerous growths:
The day I went to see the specialist I was so ill, I'd already been sick. He diagnosed me there and then with Ewing's Sarcoma - a rare type of Cancer - and told me I wouldn't be going home. I was in another world and not really with it.
After months of chemotherapy to reduce the size of the tumour from a melon to a lime, it was removed in January 2010.
After being given the all clear last month, Kayleigh is now looking forward to a bright future with her family, and had recently celebrated the birth of her nephew, Addison.