The former Liberty X singer announced the news on Twitter on Monday morning.
"..yup, myself and @hughhanley are thrilled we are expecting a mini Michelle or Hugh," the 34-year-old tweeted.
"This is a very exciting time for us after everything that's happened.. Thank you as always for your love & support! Whoop whoop! Xxxx"
Their new arrival will be a brother or sister to the couple's 18-month-old daughter Faith, who Michelle says is going to be "an amazing big sister".
The popular actress and presenter was grateful for congratulations from friends and well-wishers and replied, "Awww thank u for your well wishes. Yes, faith is gonna be an amazing big sister. She's already kissing my stomach. Have a great day all! X"
Last year, Michelle underwent a double mastectomy after discovering she had a faulty gene that made her susceptible to cancer.
When she announced the news, she also revealed that she planned to remove her ovaries.
In November, she had both breasts removed but said that she would wait for another baby before having surgery on her ovaries.