Our baby girl was 8months old with her first.
We didn't have any mess, as she cleaned it all up her self, only her bed got dirty as she got up and down in the mornings.
We just changed the top sheet, popped it in the washer and dryed it every day ( it was white, so I could keep my eye on her)
Good luck with your little girl.
Our baby was very loving and just wanted cuddles, I don't think they know what is going on with their first,jmo.
Hope she goes on alright.
Mazz
