I think Karen said it best (as usual )

I would recommend that the baby has Ashleys surname because:

- easier from an admin / medical / schooling perspective

- if dad ends up not being very involved, then there will be less reason to have to explain why she and the baby have different surnames (Personal experience - I was Cameron's "Mum" from when he was three years old, but was sick to death of having to explain to people why our surnames were different - it's almost like it gives admin / school / medical people an excuse to be nosey)

- it can always be changed to dad's name later if they do marry