with DD we were at a freestanding birth center. we were the only ones birthing there at the time, and my clothes were shed quite quickly and i labored and birthed completely naked. clothing was really not making me happy at all, so once i got into the whirlpool and back out again, the clothes did not go back on. prior to that i was only wearing a t-shirt. i'm glad there wasn't anyone else there!
with DS, he was born at home. my bottoms came off very quickly, i did have a tank top on for a little while, until i got into the shower. once again, there was no way i was going to put clothes back on once they were off
especially in my own house. so i birthed nekked that time too.
i'm assuming it will be the same with #3, since we plan to be at home. we are very open about nudity in our family, so i'm not worried about my other kids being shocked by my lack of clothes or anything like that
my advice is to do what makes you comfortable - whatever that is. remember, too, that birth is a messy business, so don't wear some sparkling white brand new night gown that you really don't want to get messed up!