The 39-year-old singer announced her pregnancy news on Chris Evans' BBC Radio 2 Breakfast Show, describing the impending arrival of her fifth baby as ''mental''.
During a chat about her new album, 'The Song Diaries', Sophie casually shared: ''The album will come out around the same time as my fifth infant because I'm having my fifth baby. Mental!''
The announcement prompted a spontaneous round of applause from the studio, and Sophie subsequently revealed she still doesn't know whether she's having a boy or a girl.
The pop star already has sons Sonny, Kit, Ray and Jesse, but she doesn't think pregnancy gets any easier the more you have.
Sophie - who has been married to The Feeling musician since 2005 - added: ''You get more relaxed with the chaos ... says the woman who just ... we just went away Richard and I with five kids, because our eldest brought a mate, and I took a book which seemed like the most optimistic thing I could have done!
''It didn't even get open - that's without baby. But I have got a two-year-old.''
Meanwhile, Richard previously admitted he doesn't think he can ''function'' without his wife.
He confessed: ''Sophie is kind, incredibly intelligent and talented. I don't think I could function without her. I'm reliant on her for counsel about work and my personal life; she always sorts me out.
''Because we have both toured, we have a two-week rule - to never be apart for longer than that. We understand each other's work and have a deep love and trust. But it is tough. We've got kids at home, and home is where we want to be.
''I still feel like I'm punching way above my weight. But I think you should feel like that about your wife.''
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