My DD1 was 7.6kg at 12 months and she is now on the 75th percentile for height and 50th for weight at 5yo - they go through growth spurts and often when they are really active they will go through a developmental spurt and then a growth spurt. If she is active, alert, developing, sleeping, drinking, weeing and pooing then she is probably just fine. Sometimes bigger babies slow down as they get older and get into their own groove as far as size and shape go. Some big babies slim right down once they start moving and end up being skinny toddlers.