The WHO growth charts for girls track weight, length (or height), head circumference, and BMI from birth through age 5. In the United States, the CDC recommends using the WHO charts for all girls from birth to age 2, then switching to CDC growth charts from ages 2 through 19. These charts show curved percentile lines that let you compare your daughter’s size and growth pattern against a healthy international standard.
What the WHO Charts Measure
For girls from birth to 2 years, two chart pages cover four key measurements: weight-for-age, length-for-age, weight-for-length, and head circumference-for-age. Each chart has a horizontal axis showing age in months and a vertical axis showing the measurement. You plot your daughter’s data point where the two values intersect, and over time those dots form a curve that reveals her growth trajectory.
BMI-for-age charts also exist in the WHO set starting at birth, but BMI tracking is not recommended for children under 2. After age 2, BMI becomes the primary tool for assessing whether a child’s weight is proportionate to her height.
How Percentiles Work
The curved lines on the chart are percentile lines. If your daughter falls on the 25th percentile for weight, that means 25% of healthy girls her age weigh less than she does, and 75% weigh more. The 50th percentile is the midpoint, not the “goal.” Half of all healthy children fall between the 25th and 75th percentile lines, and that entire range is completely normal.
What matters most is consistency. A girl who tracks along the 15th percentile visit after visit is showing a healthy, predictable pattern. A girl who drops from the 50th to the 10th over a few months is showing a change in trajectory, and that shift is what pediatricians pay attention to, not the specific number.
The outermost lines on the chart (roughly the 0.4th and 99.6th percentiles on some versions, or the 2nd and 98th on others) mark the boundaries where further evaluation is typically warranted. Only about 4 in 1,000 optimally growing children fall below the 0.4th percentile, so a measurement that low usually prompts a closer look. For head circumference specifically, a reading below the 2nd percentile after 6 weeks of age occurs in only about 1 in 250 children.
Why the WHO Charts Exist
The WHO charts are based on the Multicentre Growth Reference Study, which collected data from children in six regions: Africa, the Americas, Eastern Mediterranean, Europe, South-East Asia, and the Western Pacific. All the children in the study were breastfed, well-nourished, and raised in environments that supported healthy growth. The result is a standard that describes how children should grow under optimal conditions, rather than simply describing how children in one country happened to grow.
This is the key difference from older reference charts. The WHO charts set the breastfed infant as the normal model for growth, which means formula-fed babies may appear slightly heavier on these charts during the first year. That distinction matters because older charts sometimes made breastfed infants look like they were falling behind when they were actually growing exactly as expected.
Typical Weight Gain in the First Year
Girls gain weight fastest in the first few months, then the rate gradually slows. Between 4 weeks and 2 months, a typical monthly weight gain ranges from about 410 grams (just under a pound) at the lower end to nearly 1,500 grams (about 3.3 pounds) at the higher end. By 2 to 3 months, the range narrows to roughly 320 to 1,100 grams per month. Between 3 and 4 months, expect somewhere between 210 and 940 grams.
These ranges are wide on purpose. A girl gaining at the 5th percentile of velocity and a girl gaining at the 95th percentile are both within the normal spectrum, as long as they stay on a consistent curve. Rapid jumps or sudden plateaus are more informative than any single number.
BMI Thresholds for Older Girls
Once your daughter turns 2 and transitions to CDC growth charts, BMI-for-age becomes a useful screening tool. The categories are straightforward:
- Underweight: BMI below the 5th percentile
- Healthy weight: BMI between the 5th and 85th percentile
- Overweight: BMI between the 85th and 95th percentile
- Obesity: BMI at or above the 95th percentile
These cutoffs apply to both boys and girls, but because body composition differs by sex, the actual BMI number that corresponds to each percentile is different on the girls’ chart compared to the boys’ chart. That’s why you always interpret BMI through the age-and-sex-specific chart rather than using adult BMI categories.
Z-Scores and Malnutrition Screening
In global health settings, the WHO charts use z-scores (also called standard deviation scores) instead of percentiles. A z-score of 0 is the median, and each whole number represents one standard deviation from that median. The clinical thresholds are consistent worldwide:
- Stunting (chronic undernutrition affecting height): length-for-age below -2
- Wasting (acute undernutrition affecting weight relative to height): weight-for-length below -2
- Severe wasting: weight-for-length below -3
- Underweight: weight-for-age below -2
A z-score of -2 corresponds roughly to the 2nd percentile. If your pediatrician mentions z-scores, they’re using the same chart data, just expressed in a format that’s more precise at the extremes.
Adjusting for Premature Birth
If your daughter was born prematurely, her growth should be plotted using her corrected age, not her actual age, until at least 2 years old. Corrected age is calculated by subtracting the number of weeks she was born early from her actual age. A baby born 8 weeks early who is now 3 months old would be plotted at 1 month on the WHO chart.
This adjustment prevents premature infants from appearing smaller than they truly are relative to their developmental stage. Without it, nearly every preterm baby would fall well below the standard percentile lines, which would trigger unnecessary concern. As premature girls approach age 2, the gap between actual and corrected age becomes less significant, and most pediatricians phase out the correction.
The Switch at Age 2
When your daughter turns 2, the CDC recommends moving from WHO growth standards to CDC growth reference charts, which cover ages 2 through 19. This transition can cause a small, sudden shift in her percentile ranking even though her actual size hasn’t changed. The two chart systems were built from different populations and different statistical methods, so a girl tracking at the 40th percentile on the WHO chart might land at the 35th or 45th on the CDC chart.
This jump does not reflect a real change in growth. If your daughter’s percentile appears to shift at the 2-year visit, ask whether the chart system changed before assuming her growth pattern has shifted.