Key takeaways: Percentiles compare your baby with other babies of the same age and sex. A baby at the 10th percentile can be just as healthy as one at the 90th. What matters most is that your baby follows their own curve over time.
At every well visit, your baby is weighed and measured, and you might hear numbers like “25th percentile for weight.” Here’s what that means.
What Growth Charts Measure
- Weight.
- Length (measured lying down until age 2).
- Head circumference, which reflects brain growth.
- Weight-for-length, which compares weight to length.
WHO Growth Charts
The CDC recommends using World Health Organization (WHO) growth charts for children under 2 in the U.S. These charts describe how healthy babies grow when they’re breastfed and raised in healthy conditions, making them a standard for optimal growth.
What Percentiles Mean
A percentile shows where your baby falls compared with other babies of the same age and sex.
- 50th percentile: about half of babies are larger and half are smaller.
- 10th percentile: 10 percent of babies are smaller, 90 percent larger.
- 90th percentile: 90 percent are smaller.
There’s no “best” percentile. Genetics play a big role: tall parents often have long babies, and small parents often have small babies.
The Trend Matters Most
Pediatricians look at how your baby’s growth changes over time. A baby who stays near the 10th percentile, growing steadily, is usually doing well. Concerns arise when:
- Growth crosses two or more major percentile lines downward or upward.
- Weight is very low or very high compared with length.
- Head growth is too fast or too slow.
It’s normal for babies to shift percentiles in the first months as they find their genetic growth pattern. Breastfed babies sometimes look different on growth charts than formula-fed babies; the WHO charts account for this.
Premature Babies
For premature babies, growth is plotted using adjusted age (age from due date) until about 2 years. Some NICU teams use special preterm charts first.
Typical Growth in the First Year
- Weight: most babies regain birth weight by 10 to 14 days, roughly double it around 4 to 6 months, and roughly triple it by 12 months.
- Length: babies grow about 10 inches (25 cm) in the first year.
- Head circumference: grows quickly in the first months, then slows.
Questions to Ask
- Is my baby following their curve?
- How does weight compare with length?
- Is head growth on track?
- Should we change anything about feeding?
Talk to your baby’s doctor if: your baby isn’t back to birth weight by 2 weeks, seems to be losing weight, has fewer wet diapers, is feeding poorly, or if you have concerns about growth.
The Bottom Line
Percentiles describe where your baby is, not whether they’re healthy. Steady growth along their own curve is what matters most.
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Sources
- Grummer-Strawn LM, Reinold C, Krebs NF. Use of World Health Organization and CDC growth charts for children aged 0-59 months in the United States. MMWR Recomm Rep. 2010;59(RR-9):1-15.
- WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards based on length/height, weight and age. Acta Paediatr Suppl. 2006;450:76-85.
- Centers for Disease Control and Prevention. Growth charts: WHO growth standards. https://www.cdc.gov/growthcharts
- Hagan JF Jr, Shaw JS, Duncan PM, eds. Bright Futures: Guidelines for Health Supervision of Infants, Children, and Adolescents. 4th ed. American Academy of Pediatrics; 2017.
- Fenton TR, Kim JH. A systematic review and meta-analysis to revise the Fenton growth chart for preterm infants. BMC Pediatr. 2013;13:59.
This article is for general education and is not a substitute for individualized medical advice. Always talk with your baby’s health care provider or your own provider about your specific situation. If you think your baby or you may have a medical emergency, call 911.
