Pretty much what the title says, my 2.7 year old DD has suddenly started waking at 5/5.30 every morning. She used to sleep until 7/7.30.
She goes to bed around 7/7.30pm and has a nap after her lunch around 1pm.
This routine has been fine for about a year and all of a sudden she's up at the crack of dawn! 
I have blackout blinds and blackout curtain liners in her room.
I'm expecting DD2 in 4 weeks so this is the worst time for her sleeping habits to change.
Does anyone have any advice?