My mom did the same as well DD & I wore the exact same outfit for our first Santa pictures (but 24 years apart), I also have the dress I wore to my first Sunday at Church, my first Christmas dress, my first Easter dress and my 1st birthday dress as well as a little sweatshirt that was my mom's college Alma Mater and a sweater someone knitted for me.
Re: save your LO's special outfits
I am saving a few things for her to keep, but some other clothes through the first year that I want to eventually make a quilt out of for her.
Everything my mom attempted to save got destroyed by either a fire, or flood. Boo!