The 'What About Us' singer has been told not to perform with the group again until after her baby has arrived.
That means she won't be performing with Mollie King, Rochelle Humes, Vanessa White and Una Healy at Bluewater Shopping Centre on 10 August or at this year's Virgin Media's V Festival on 17 and 18 August.
Confirming the news on Twitter, Frankie said: "Hey guys, really sad I won't be there for the next few gigs, as I've been advised not to perform by my doctor until after the baby arrives."
Hey guys, really sad I won't be there for the next few gigs, as I've been advised not to perform by my doctor until after the baby arrives.— Francesca Sandford (@FrankieTheSats) August 8, 2013
Frankie added: "But don't worry, I know my other 4 Sats will totally rock it while I'm resting the bump. I'll be back ASAP!"
The singer and her footballer fiancé Wayne Bridge, who plays for Reading, announced in May that they are expecting their first child together later this year. They had become engaged the previous month.
They have already confirmed it will be a baby boy and were seen out shopping for baby supplies together earlier this week.
Frankie had been hard at work with The Saturdays as normal until her announcement last night, recently joining them to film their new music video 'Disco Love'.
More pregnant celebrities in our gallery below!
Copyright: Vimeo / Weiss Eubanks