My Brylee girl is 13lbs and she was born on 9 June so I guess she is on the smaller side. She is 25 inches (or 63cm). At her 4 month check they said they are a little concerned at her head measurment as it has dropped off the curve a bit. I spoke with a friend who is a midwife and she said, they shouldn't measure heads anymore as the measurments are inconclusive and dont really mean anything anyway. As long as they are doing what they should, feeding, sleeping, pooping, putting on weight, and reaching their milestones, then all is good!