Size 24 Sophie Bird went to her GP 10 times complaining of stomach pains.
But she was so overweight, doctors failed to spot that she was carrying a baby.
It wasn't until two days after she was a bridesmaid at her friend's wedding in September 2010 that she visited her doctor again with severe stomach pain.
She was referred to A&E where an examination revealed she was 38 weeks pregnant. But not only that: she was 4cm dilated and in labour!
"I had managed to carry a baby without changing shape or size for nearly nine months. I had been fitted for my bridesmaid dress in May and the dress still fitted in September - just before I gave birth."
She said she had visited her doctor 10 times without a clue she was expecting.
She said: " I was on the pill, and as a child I'd been diagnosed with polycystic ovaries - they told me I'd need help to conceive, so it never dawned on me that I could be pregnant.
"Two days after Aimee's wedding, I was in so much pain at lunchtime that I rang the doctor and made an appointment for 5pm.
"This time, the doctor did a pregnancy test and confirmed I was pregnant, but no-one knew how many weeks.
"The doctor sent me of to A&E where I had an internal examination. I was told I was 4cm dilated and in full labour.
"Straight away a porter put me in a wheelchair and pushed me across the car park, at some crazy speed, to the maternity unit. It was all nuts, I couldn't believe what was happening."
Four hours after learning she was pregnant, baby Rowan was born at 9pm.
Sophie, 32, from Milcombe, Oxfordshire, said: "It was completely surreal. One minute my life was normal, next minute I had a beautiful little baby boy.
"I had no baby stuff so my friends and family rallied round to get me all the baby equipment - they were amazing."
Sadly, the joy of Rowan's arrival was tinged with pain soon afterwards when Sophie discovered that her baby's dad – who she'd known since she was 17 - had been cheating on her with her best friend.
She said: "It completely broke me. I kicked him out and was so traumatised and so stressed by it all that I couldn't face eating.
"I felt constantly sick, and as a result my size started to shrink. I knew that this was the right time to get control back of my life, my body, my mind and my eating."
Sophie had tried diets before but failed to stick to them, but this time, she said: "I set my mind to losing the weight and vowed never, ever put it back on.
"I took up Morris Dancing and Roller Derby to keep active. I also joined the gym and made sure I did some form of exercise every day.
"I changed my diet to fresh, healthy food and limited my portion size.
"The weight started to drop off me. I lost five stone and was feeling fantastic - energised, happy and confident."
In May, a friend told Sophie about Malory Band, a new way to monitor and motivate weight loss.
The device - the brainchild of former Rally Driving Champion and TV presenter Penny Mallory - is a narrow cord that sits around the waist and starts to feel tighter as a person eats.
It acts as a 'psychological alarm bell', triggering the brain to think about the amount of food it needs.
Sophie, who has lost eight stone and plans to shed another two stone by next summer, said: "It was just what I needed. I wish I had known about it before.
"I love it because it's not a diet. I make all the decisions about what I eat and my Malory Band reminds me when I have had enough to eat. It's so simple and so effective - everyone should have one.
'When I started wearing the Malory Band, it would start to feel tight when I ate, and so I'd stop eating.
"It made me realise I didn't need to carry on eating, and the weight came off so quickly. I was still having a healthy diet, but the band was literally reining me in and making me constantly aware of what I was putting into my body.
"I can't express how happy I am about losing the weight. I have more confidence and energy and am a much happier person.
"Before, I'd go out with my friends and just want to hide away as they were all so slim and healthy.
"I feel alive and I am so much happier. And of course, now I have my wonderful Rowan, he's the sunshine in my life."