Yep, our 18-month-old munchkin started this a few weeks ago. It's fun, isn't it?
From what I've been told by friends, they do go in phases with SA, like what aclee posted.
__________________
Lori
Mom to TWO angels:

An angel in heaven,
Rachael Marie (05/09/05 - 01/06/06) - taken from this earth far too soon due to complications from her diagnosis of Spinal Muscular Atrophy, Type I

An angel on earth,
Isabella Grace (born 07/03/07) - placed in our arms 1 hour after birth, through a wonderful open adoption
Hoping to adopt again down the road...