According to The Sun, Willougby is due to leave the ITV magazine show in two weeks' time. The presenter and husband Dan Baldwin are expecting a baby girl next month.
Falconer will take turns with Ruth Langsford to join Phillip Schofield on the weekday programme. The 35-year-old announced that she is also pregnant with her first child last month.
Schofield said: "I will really miss Holly and wish her a safe delivery."
Fiona Phillips was previously linked to the role along with GMTV newsreader Helen Fospero.
Falconer added: "I've always been a fan of the show."
This Morning continues weekdays at 10.30am on ITV1.
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