I didn't wash everything until about 38 weeks, I figured if I washed it any earlier I'd just want to wash it again close to bub's arrival anyways. DD was 8lbs at birth, lasted about 5 days in 0000 then went to 000. Just yesterday (6wks old) we moved up to 00 wondersuits, all her other 00 stuff is too big, but the wondersuits seem smaller sizing. HTH