'I'm not desperate, but a girl would be nice as part of the family.
Coleen's spouse Wayne Rooney quickly retweeted the message but has yet to comment on the pregnancy news himself.
Coleen's message appears to relate to the recent publication of bikini photos, which led to speculation over whether she was expecting.
Yet she did let on that's she'd had her first scan, which usually occurs around 12 weeks, but can vary a few weeks either side.
She told new! magazine: 'I can imagine having a girl.
Before she knew she had another little boy - Kit, born in January 2016.
The Littlewoods ambassador revealed little details to her loyal fans.
Taking to Twitter, she wrote: 'So Happy!.
Although Coleen has never outright denied the news, the fashion designer recently laughed off rumours she was going to be a mum again on social media, telling her fans: 'So basically....yes on holiday again...yes I've put weight on...'
She said: "People go on about, 'Don't you want a girl?' but I'm not desperate for a girl. I'm used to having boys about". I quite like being the only girl in the house and I'm happy with what I've got.
"You can try for a baby and whether you have a girl or a boy is a different matter".
"Whether I did have another one, I wouldn't mind whatsoever". She's got five of them so yes, she would like a girl.
Coleen's commitment to her family recently saw her named McDonald's Football Mum of the Year.