Sarah - I'm certainly no expert but I think I read somewhere that they only gain a few kgs a year after they turn 1? Lucie was 8.8kg at 12 months and only now has hit the 10kg mark at 19 months!

If they kept gaining weight like they did as newborns they'd probably weigh as much as us by now.

Oh and make sure you compare height too - he's probably growing like a weed now, long and lean!