You know...it might have been even smarter to just show the birth of Luke...not show Leia's birth, although it happens with a minute. That way, when future generations watch these movies in order, it would STILL be a shock to find out that Luke and Leia are twins. But I really, really have no clue how you could film that or script that. It could become one of those classic Legend of Zelda moments- "But Link, Zelda is your....!"