The 23-year-old British singer, who married JLS hunk Marvin Humes in England on 27 July (12), announced her happy news on Thursday (22Nov12).
In a post to fans on Twitter.com, she writes, "I wanted to be the first to tell you... we have some exciting news to share! Marvin and I could Not be more thrilled to announce that we are expecting our first child mid next year.
"We have always dreamt of being parents and the news is the best early Christmas present we could have asked for. I know Marvin is going to be a great dad and we're so excited to start a family."
Humes is the second member of the girl group to become a mum - Una Healy gave birth to a daughter, Aoife Belle, on 13 March (12).
Healy congratulated her pal via Twitter, writing, "So happy to be able to share the amazing news Rochelle and Marvin are expecting a baby! Mini sat number 2 on the way," and fellow bandmate Mollie King added, "Couldn't be more excited and thrilled for Rochelle & Marvin!!! Ahhh can't believe this!! Who else feels The Sats Juniors forming?"