Healthy babies come in different shapes/sizes.
Your pediatrician will monitor growth from the start with weight, length, head measurements. Predictable patterns will emerge: birthweight doubles by 5 months; triples by 1 yr.; birthlength increased by 50% by 1yr. Fastest growth is in the 1st 6 months of age (5-7 oz/week; 1/2-1 inch/month). Slower after (3-5 oz/wk; 3/8 in/mos).