The 28-year-old singer tweeted last night letting fans know the baby was on its way, slowly but surely.
She wrote: "Slow labour, feeling pretty blue in hospital everything is fine just need to rest and stay patient my angel will come soon xxx"
Rebecca previously revealed she is expecting a girl, and it is thought she will call her Arabella.
The former X Factor contestant has been with the father for over a year, but has never publicly spoken of him.
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She is already mum to daughter Lillie May, nine, and seven-year-old Karl from a previous relationship.
It was after collapsing on Loose Women in April that Rebecca found out she was pregnant again.
In June she told the Daily Mail: "What's funny is after the show, I took text because I was thinking 'This is weird, what's going on with my body?' and it came up negative.
"I was like 'How strange!' I've got all of the pregnancy symptoms but after the show I ended up spending two days resting in bed. I kept saying to everyone, I've got pregnancy symptoms so it was really weird and then a couple of days later I took another text and it was positive!"