I used mine from around 8lbs after he lost his cord stump. The fit from the beginning though, I just had cute newborns. It wasn't a week or so before he was out wetting the newborns and into the BG. Used the nb inserts for awhile but not long.
Wife to 1
, L 12-02, B 7-05, J 2-07, L 12-08, S 10-10,
and Q 5-29-12