"Hi everyone! I wish to announce that today I have officially changed my name to Una Foden :) #theartistformallyknownashealy" she told her 755,000 followers.
Una, 32, and Ben, 28, tied the knot in her native Ireland in June 2012, but until now she has chosen to go by her maiden name.
Her change of heart means she now has the same family name as her husband and their little girl Aoife Belle Foden, who was born in March 2012.
Meanwhile, The Saturdays are eagerly awaiting the arrival of another mini member to join Aoife and Rochelle Humes' five-month-old baby girl Alaia Mai.
Frankie Sandford, 24, is due to give birth to her little boy with Wayne Bridge any day now.
Speaking at Tuesday's Attitude Awards afterparty, Una said the band were all waiting by their phones for news of the birth.
"The phone is on silent," she said. "We're waiting because it's literally coming in the next few days. (She's due) any moment now.
"All of us will (get the call). She'll definitely send out a group text or something."
Rochelle, 24, has also revealed that The Saturdays have made a pact not to go on tour until Frankie is back from maternity leave.
"She would absolutely kill us if we went on tour without her," she told BBC Radio One.
"It's her favourite thing to do so we'll all be there together. It'll be the five of us back in force together on tour."