I think they are all different, but I know AprilLove hit 3 lb 2 oz, just over 7 months old, and she gained another 10 oz between 7 and 13 months. She's 16 months now and has stayed at 3 3/4 since 13 months. Her parents were 3 and 5 lbs.
Forgot to add, she hasn't really gotten bigger as far as size, she just filled out, more "meaty" |