She did it before she learned to sit supported by her hands & even after, when she was learning to sit unsupported. I think it's just the way the kids learn how to control their stomach & back muscles to help them sit up. Holding Jackson's hips while he's sitting helps him train his stomach & back muscles to work in conjunction to sit upright without support. Keep doing it! If you have a Boppy or even some pillows on the sides & behind him, in case he throws himself backwards, that will help him also. I thought Sarah was the only one who seemed a glutton for punishment with throwing herself backward.
HTH!
Amanda
Emma 12/10/99
Sarah (Ds) 4/20/04
