'The Sats baby is growing': Frankie Sandford comes to grips with Una Healy's bump as she returns after illness

By Alanah Eriksen

Last updated at 3:28 PM on 3rd November 2011

It wasn't long after Una Healy announced she was pregnant that bandmate Frankie Sandford went into hiding with a mysterious illness.

So no doubt her growing baby bump was a shock for The Saturday's singer when she reunited with the redhead this week.

The 22-year-old shared a cute picture in which she is seen wrapping a tape measure around Una's stomach.

You're finally showing! Frankie Sandford playfully wraps a tape measure around her band mate Una Healy's pregnant belly

She joked: 'I've been very impatient for Unas bump to show. I've come back and it's finally here! The Sats baby is growing!!!!! :) '

Frankie was admitted to hospital in October, and although reasons were unclear, a spokesperson insisted the treatment had nothing to do with drugs, alcohol or cosmetic surgery.

She was seen for the first time in two months yesterday outside the ITV studios in London.

But the night before she was nowhere to be seen as the rest of the band were busy revelling in the limelight as they switched on the Christmas lights in central London.

Back to work: Frankie Sandford is pictured outside the ITV Studios in London

Back to work: Frankie outside the ITV Studios in London yesterday, pictured for the first time after two months off work

Fighting fit: The 22-year-old has been out of action for the past two months with an undisclosed illness

Yesterday, stunning Frankie looked healthy and tanned under the cover of a felt hat and aviator style silver-rimmed sunglasses.

She matched her grey trilby with a fur-collared winter cardigan, black jeans and a black vest top.

Frankie flashed a smile to waiting photographers as she headed out to a waiting car which whisked her off to rehearsals with the rest of the group - Una, Mollie King, Rochelle Wiseman and Vanessa White.

It will only get bigger! Frankie tweeted her excitement about her Una's stomach

Her smile wasn't the only sign of her happiness at being back on her feet and in the public realm once again.

Frankie also took to Twitter to express her delight at heading back to work.

She said: 'Just been watching some of your get well soon videos. thanks for all the hard work messages! i shall be with my @TheSaturdays today!excited!'

A tiny bump: Una still sported a trim physique despite being pregnant with her first child to Ben Foden

A tiny bump: Una still sported a trim physique on Tuesday night as she and the rest of her bandmates turned on the Christmas lights on Oxford Street

The band on Tuesday lit up London's Oxford Street with cheers from the waiting crowd braving the cold as they chanted for the pop princesses.

They joined Toby Anstis and U.S. duo The Pierces, who have already made a name for themselves in their native America and are trying to win over UK fans.

Mother-to-be Una, 30, showed off the slightest hint of a bump in a black tasselled skirt from Missguided.co.uk, although her silhouette still looked svelte despite expecting her first child with Ben Foden in 2012.