The Girls Aloud singer is delighted her former bandmate and longterm boyfriend Justin Scott are expecting their first child together, but she didn't expect the happy news to come so quickly after another ex-member of the group, Nadine Coyle, welcomed her baby girl into the world.
Talking on British chat show 'Lorraine' she said: ''I think we all expected Kimberley to be the first one and I kind of thought if it's going to be anyone, it would be Kimberley next but I didn't expect it so soon. ''
While Sarah is happy in her relationship with DJ Mark Foster, she isn't ready for motherhood yet.
She explained: ''Apparently I'm next in line ... not yet, not yet though. Maybe one day ... I have a few more boxes to tick.''
Quizzed on being an honorary auntie, she added: ''Yes I know, and I have three god children as well so that's enough for now.''
Though the 'Promise' singer has been dating Mark for just under two years, they have known one another since they were teenagers and she says their shared history is good for their relationship.
The 32-year-old beauty said: ''It does help, there's definitely a lot of trust involved and he's not one of these 'yes people', he'll tell me if he thinks I'm wrong.''