It's real, but it's also (at least recently) easy enough to keep people from dying of it. The symptoms also mimic that of a massive heart attack, so what happened with Padme isn't exactly the same thing.
She could've easily died during child birth or from her injuries from Anakin, but no, GL had to make her "lose the will to live". So, a woman that's been a strong Queen, fought in wars, and represented her people as a Senator, doesn't have the will to live to 1) attempt to bring her husband back to the light side and 2) take care of the children she just bore. I don't think so.