Baby Growth Charts – One Month

Baby Growth Charts - One MonthThe World Health Organization and the U.S. Centers For Disease Control and Prevention release baby growth charts for use by pediatricians in tracking the length, weight, and head circumference of children. The World Health Organization growth charts are used from birth until age 2 while–in the U.S.–the CDC growth charts are used from age 2 until age 19.

For babies from birth until age 2, the World Health Organization growth charts are reformatted for ease of use by the CDC. There are four separate baby growth charts:

WHO Growth Chart for Boys: Length-for-age and Weight-for-age
Raw Data Table

Boys Length-for-age and Weight-for-age

WHO Growth Chart for Boys: Head circumference-for-age and Weight-for-length
Raw Data Table

Boys Weight-for-length and Head Circumference-for-age

WHO Growth Chart for Girls: Length-for-age and Weight-for-age
Raw Data Table

Girls Length-for-age and Weight-for-age

WHO Growth Chart for Girls: Head circumference-for-age and Weight-for-length
Raw Data Table

Girls Weight-for-length and Head Circumference-for-age

Using the Baby Growth Charts

The WHO Baby Growth Charts may be difficult to understand at first glance. I spent some time analyzing my baby’s measurements in order to read the charts. The raw data tables link to unformatted percentile tables for easier comparison. Unfortunately the data tables use the metric system while the charts have both imperial and metric measurements.

Weight
My daughter’s initial birth weight was questionable, but I know she weighed 7lb 7oz at 6 days, 8lb 2oz at 13 days, and 10lb 6oz at 1 month. I refer to chart “Girls: Length-for-age and Weight-for-age“. The bottom half of that chart is used to track weight based on age. The top of the chart indicates the baby’s age while the bottom half / left hand side indicates the baby’s weight. I assume my daughter was close to 7lb 3oz at birth, so I start with the “Birth” vertical line and follow it down until the bottom half of the page.

The horizontal lines snaking upwards and to the right show percentile ranges. 96 percent of babies fall within the horizontal lines at every age range. The bottom horizontal line equals 2.3rd percentile (the baby is heavier than 2.3 percent of babies at that age) while the top horizontal line equals 97.7th percentile (the baby is heavier than 97.7 percent of babies at that age). The middle, darker horizontal line equals 50th percentile (the baby is heavier than 50 percent of babies at that age).

In my daughter’s case, 7lb 3oz (3.26kg) at birth falls just above the middle, darker horizontal line meaning she was somewhere between the 50th and 75th [the next higher line] percentiles. At 1 month, she was 10lb 6oz (4.71kg). I move one, light vertical line over at the top of the chart to find one month and track it down to the bottom half. Her weight puts her between the 3rd and 4th lines from the top, meaning she is between the 75th and 90th percentiles.

Length
My daughter’s initial length at birth was 19.25 in. She measured 20in at 6 days, 20.1in at 13 days, and 20.75in at 1 month. I use the top half of the chart “Girls: Length-for-age and Weight-for-age” and follow a similar procedure as for weight.

My baby’s length of 19.25in (48.90cm) at birth places her between the 25th and 50th percentiles. Her 1 month length of 20.75in (52.71cm) places her between the 25th and 50th percentiles.

Head Circumference
We did not receive an accurate head circumference measurement at my daughter’s birth. Her head circumference at 1 month was 34.8cm. I use the top half of the chart “Girls: Head circumference-for-age and Weight-for-length” and follow a similar procedure as for the weight and length.

My baby’s head circumference of 34.8cm (13.70in) at 1 month places her between the 5th and 10th percentiles.

One Month

I would prefer my daughter to be exactly at the 50th percentile in all three areas. Her weight is a little high, but nothing for us to be concerned about. Her length is a little low, but given her parents’ heights, we are not concerned about it either. Her head circumference is a concern for us even as our pediatrician counsels us not to worry. My wife and I suspect that the vacuum extraction used in her delivery contributed to her small head circumference and we both hope that her head will grow normally over time. However, for now I am still concerned that my baby’s head is too small.