Pyro, thanks for this. I think that Protestants generally have a more gnostic way of understanding most things, including virginity. Virgniity for them is only not having had sexual intercourse. That is part of the reason why it is irrelevant for them how Jesus's birth physically affected Mary, because for them there is no such thing as "physical virginity". Virginity is wholly extrinsic to the condition of the body; it is rather an extrinsic property, i.e. the property of not having engaged in or participated in some act.
Of course, most Protestants don't accept the perpetual virginity of Mary even according to the gnostic sense of virginity.
-A8