20 MO sleep woes...

Need advice on if this stage will pass.  My 20 month old is great at going to bed, we put her down around 745 and she falls asleep by 815.  In that 30 min she rolls around, talks to herself, and just winds down.  The issue we are having is that the past 2 weeks she has been waking at 4-430 and just babbling to herself.  She will squeal, babble, make noises etc.  She usually falls back asleep by 530-6AM.  I am not sure what to do.  I don't go in there because she is not upset, but I worry about the lack of sleep and such a long wakeful period.  ANy ideas on what could be causing this?  My only guess is she is really starting to talk up a storm so wants to practice.