No, don’t stress. Percentiles are the major tool a pediatrician uses to make sure baby is growing at a healthy rate. Your child’s height, weight and head circumference are plotted on a growth chart at each checkup. That chart is based on averages for baby’s gender and age, but it doesn’t mean that anything is necessarily wrong if baby falls into the high or low range.
“What really matters is that his percentiles stay in the same range from visit to visit,” says pediatrician Preeti Parikh, MD. For example, if he starts out at the 50th percentile for height, weight and head circumference — which is considered average — and then moves to the 90th for head circumference while everything else stays the same, this could mean there’s a problem. If baby was born preterm, the doctor will use gestational age to plot his numbers.
These are the averages (known as the 50th percentile) for baby’s first year, according to the World Health Organization:
1 month: 21.5 inches long, 9.9 pounds, 14.6-inch head circumference
2 months: 22.9 inches long, 12.3 pounds, 15.4-inch head circumference
4 months: 25.2 inches long, 15.4 pounds, 16.3-inch head circumference
6 months: 26.6 inches long, 17.6 pounds, 17-inch head circumference
9 months: 28.3 inches long, 19.8 pounds, 17.7-inch head circumference
12 months: 29.8 inches long, 21.2 pounds, 18.1-inch head circumference
1 month: 21.1 inches long, 9.4 pounds, 14.4-inch head circumference
2 months: 22.4 inches long, 11.3 pounds, 15-inch head circumference
4 months: 24.4 inches long, 14 pounds, 15.9-inch head circumference
6 months: 25.8 inches long, 16.1 pounds, 16.5-inch head circumference
9 months: 27.6 inches long, 18.1 pounds, 17.3-inch head circumference
12 months: 29.1 inches long, 19.8 pounds, 17.7-inch head circumference
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