In ROTJ, at the Ewok Village Luke asks Leia what she remebers of her real mother. He asks her this because he knows she is his sister and wants a little insight before he breaks the news to her that she is his sister and that Vader is their Father. Leia's reply was that she died when she was very little, but, Leia remebered that she was beautiful, but Sad! Now, some people do have memories from ages of 1 or 2, but, to be able to pick out emotions points to an age of 4 or higher I would think, so if Leia is capable of determining and remembering her mothers emotional state, and that she was also beautiful, leads me to believe that Amidala lives for at least 3 to 4 years after Luke and Leia are born. So Anakin obviously has turned to Vader in that time! Unless Lucas pulls a fast one and gives us the certain point of view stuff.
It has been a long, LONG debate rehearsed on these boards muchly before- the thematic appropriateness of Padme dying versus the sheer practical continuity of it not being possible due to Leia's words in ROTJ. There are plenty of ways that you could say it happens- the film covering a longer time span than normal, some sort of epilogue section, weird super-memories from Leia the Jedi- but still, before we hear any diferent, the most likely scenario is that she dies between trilogies.