Your going to be busy 5 litters!
I would try to seperate them if poss, just use some plastic posts and electric wire. Gilts have a funny habbit of trying to farrow together! You may also have 2 decide they want the same ark and end up with 1 farrowing outside not good in november!
That said you may be lucky and get away with it, but your better to be safe than sorry, how much land are they on?