I don't think it matters what you wear in labour because your top can always be lifted up and bubby put straight on your chest after birth. It gives bub heaps of access for a breast feed or alternatively you can just take your top off after bub is born.
Wear whatever you will be comfortable to labour in as that is really important. Like I said whatever you wear can be taken off in the matter of a few seconds. This is what the huge majority of ladies I look after in labour do.
The other thing I suggest to pg women is to wear something that you don't mind if it gets thrown away as it can get quite dirty/bloody after the actual birth.
I personally laboured in my knickers and a t-shirt (white of all colours, LOL!!) but got nudie for the shower and stayed that way until my shower after DD was born. Like the girls said it is much easier than worrying about clothes which I found really weird as I'm the biggest prude going around but I was stark naked in front of ladies/drs I work with.