Robyn Bailey had blamed her expanding waistline on being happy in a relationship.
She was taking the contraceptive pill, had regular periods and therefore never imagined she could be pregnant.
Robyn, 23, drank and smoke and two weeks before she went to see a doctor thinking she had appendicitis she had been out celebrating her birthday and had binged on alcohol.
She was shocked to discover the agonising pain she was experiencing was a sign she was in labour.
But the emotional rollercoaster was far from over for the new mother and her partner Luke Darvill.
Just weeks after welcoming their surprise baby into the world, their joy turned to panic when they discovered Daisy struggling to breathe.
The child was rushed to hospital and diagnosed with two holes in her heart. Daisy nearly died three times, during two lots of heart surgery
Looking back at the tumultuous time, Robyn, from Haverhill, Suffolk, recalled: 'I had gone up from a size 12 when I started dating Luke to a size 18-20 three years later,' she said.
Robyn Bailey says having Daisy by surprise then nearly losing her was a 'rollercoaster'
The 23-year-old blamed her pregnancy weight gain on being happy in a relationship
'I just thought it was "relationship weight," gained because we were so happy together and I hadn't been watching what I ate.
'I was on the contraceptive pill and didn't miss a period.'
'I couldn't stop crying'
In February 2015, barmaid Robyn and logistics co-ordinator Luke, 26, were staying over at his father's house, when she woke with agonising stomach pain.
Because she had no idea she was pregnant, when her waters broke, she thought the pain was an appendicitis.
Robyn and Luke say Daisy, now two, has come on leaps and bounds after her operations
'I told Luke some mess had come out of me,' she explained. 'He misunderstood and thought I had soiled myself. He told me to clean myself up.
'We'd earlier that night had an argument over KFC, so we were in a bad mood with each other.'
But, in agony, Robyn couldn't sleep and called the NHS helpline, 101, who asked if she could be pregnant.
'I said no straight away,' she continued. 'I hadn't missed a period, so I didn't think I was.'
The next morning, still in pain, the couple went to the doctors and were amazed to be told Robyn was expecting a baby 'at any minute'.
Daisy had an elastic band-style object round her valve, so her heart could function properly
They went straight to Addenbroke's Hospital in Cambridge.
'I couldn't believe it, I couldn't stop crying,' she said. 'I was in shock and just kept crying and crying and crying.
'I celebrated my 21st at seven months pregnant and drank loads. Two weeks before I gave birth I was out celebrating a friend's 21st.
'I drank and smoked while expecting. It's not something I'd encourage, but I simply did not know I was pregnant.'
Taken to hospital by car, it was confirmed she was pregnant - even possibly overdue - and was dilated by 2cm.
But, after 26 hours of pushing, the baby still hadn't arrived so Robyn was given an emergency caesarean.
The child had to have a second operation, a heart bypass, at Great Ormond Street