The singer showed off her baby bump at 'The Hangover III' premiere in London on Wednesday, as she posed for photos alongside her bandmates.
The 24-year-old, who it feels like only just announced her pregnancy, wore a floor-length silver and white dress with a silver clutch purse.
Sandford announced she and her footballer fiance Wayne Bridge were expecting a baby by posting on Twitter: "Some big news from me today! Wayne and I are having a baby. We are both SO happy and can't wait for his or hers arrival!"
Frankie is the third member of The Saturdays to fall pregnant, Una Healy is already mum to one-year-old Aoife Belle, and Rochelle Humes gave birth to a baby girl on Monday morning.
The singer and husband Marvin Humes have named their new daughter Alaia-Mai Humes.
See all the snaps from The Hangover III premiere below...