a couple of the novels written after Episode III was in theaters seem to strongly hint at the Emperor knowing through the Dark Side that Anakin/Vader hadn't actually killed Padmé when he Force choked her on Mustafar and that she had indeed survived for a short time after the incident.
Which novels? I've admittedly skipped many of them but I never came across that. Dark Lord
, for example, indicates the opposite: Not for the first time Sidious wondered what might have happened had Anakin not killed Padme on Mustafar.