Ferber Experts, I need some advice

mrsadamc 05

Ok, so about a month ago (maybe month and a half) we did Ferber with Katie.  It went really well and we went from 2 or 3 wakeups a night to 0.  And she got really good about just going to sleep.  

For the last weekish she has been getting up every night at 4am.  Her normal wake up is between 5:30 and 6.  

What do you think could be the cause of this?  I have to do progressive waiting to make this stop again, right?  So if I do, do I start with 3 or 4 minutes of wait time again or can I start with something longer, like 10 minutes?  

I don't remember reading anything about this in the book but I was so sleep deprived when I read it I could have and just don't remember lol!