Ditto Erica09M. Many convertibles have bottom slots that are too tall for most newborns. My ds was a preemie and weighed 5# when he came home from the hospital and his little infant seat was almost too big for him, so I think it's a little rediculous when some of these seats say that they are rated from 5#, but I digress...
I understand that convertible seats the generally fit newborns well are the Cosco Scenera 5pt (very basic, no extra padding or EPS/EPP foam, but a decent inexpensive seat that has 7" bottom harness slots), the Evenflo Triumph Advance version that comes w/the infant padding, The First Years True Fit and the Sunshine Kids Radian w/the SK Comfy Soft insert (the 65 lb version of this seat doesn't come with it, but it can be bought seperately and is approved by the mfgr. All the Radians have the same measurements just different features and weight limits).
hth