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Baby Weight Tracking: How to Read a Growth Chart

Is my baby gaining enough weight? How growth percentiles actually work, what growth spurts mean, and which signs genuinely warrant a call to the pediatrician.

Reviewed by: Whispie Editorial Team Evidence-Based Parenting Research

Published: 2026-04-06

This article is for general information and is not a substitute for professional medical advice. Always consult your pediatrician or doctor about your child.

Sources: WHO, CDC, AAP and NHS guidance. Recommendations differ between countries — for local advice see the NHS or CDC.

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What Percentiles Actually Mean

A growth chart compares your baby to a reference population of the same age and sex. Staying on top of these tracking appointments can be a challenge for busy families — the working parents guide has practical tips for scheduling and sharing health responsibilities. The 50th percentile is the median — half of babies are above, half below. Being at the 10th percentile doesn't mean your baby is unhealthy; it means they're on the smaller end of normal. What matters most is the trend over time, not any single measurement (WHO Child Growth Standards, 2006).

Consistent tracking along a percentile line — even a low one — signals healthy growth. It's sudden drops or climbs across two or more major percentile lines that warrant evaluation.

Free tool: Baby Age Calculator: How Many Weeks or Months Old Is My Baby?

Normal Weight Gain by Age

First weeks: The NHS says it is normal for babies to lose some weight in the first few days, and that most babies are at or above their birth weight by 3 weeks. Your baby is weighed during their first 2 weeks to check.
Up to 6 months: The NHS says healthy babies should be weighed no more than once a month up to 6 months, unless you ask for it or there are concerns, and each weight goes on a centile chart in the red book.
6–12 months: Growth naturally slows compared to the early months. This is normal and not a feeding problem.
After the first year: Growth slows further, and appetite becomes more variable.

Growth Spurts

Some babies go through periods of wanting to feed more often, seeming fussier and sleeping differently. UNICEF UK and the NHS say to feed your baby as often as they want and for as long as they want. If you are worried that your baby is not getting enough, check their nappies and weight against the signs in is my baby getting enough milk? and ask your midwife or health visitor.

When to Be Concerned

Has not regained birth weight by 3 weeks of age (NHS)
Drops across two or more major percentile lines
Fewer wet diapers than usual, or fewer than the NHS's at least 6 heavy, wet nappies a day from day 5
Persistent crying and apparent hunger after every feeding