Firstly, I did not even know or realise that Martha-Louise was pregnant or that they were interested in having more children...Usually (in my experience of talking to people) those with 2 of a kind (two boys or two girls) usually don't have a third child for risk of having "3 of a kind"...but Ari and ML are obviously risk takers and three girls is gorgeous no matter what anyone says...
Now as for their names...love them all...Maud is the name of a Norwegian Queen...and in response to Ella Kay's comment about American names give to Norwegian royal babies...well, I think all middle names have some American associations, even if their origins and meaning are not American...
Maud Angelica - I think of Queen Maud and Angelica Huston
Leah Isadora - They (A & ML) like Princess Leia (Star Wars); Isadora Duncan, was she American?
Emma Tallulah - Emma is a nice simple name to match Maud & Leah and I think of lots of things when I hear Tallulah...Tallulah Bankhead, Tallulah Willis, and Tallulah the chicken from the Maisy series of books by Lucy Cousins...
I like the combo of plain and simple first name with unusual and longer middle names..very cool!!!