Baby Weight Gain: Growth Charts, Weight Table by Age and When to Worry
Dra. Paula Andrade
CRM-SP 204778 | RQE 131771 | Título SBP 2024
Licensed in Brazil — Itaim Bibi, São Paulo
One of the biggest concerns parents have in the first months of a baby's life is weight gain. "Is my baby growing well?", "Is the weight in the right range?", "What do these percentiles mean?" — these questions come up in nearly every well-child visit. In this guide, you will learn how the WHO growth chart works, what is normal at each stage, and when it truly makes sense to worry. For expat families in Sao Paulo, understanding how pediatric care works in Brazil will make growth monitoring much less stressful.
Quick Summary
→WHO growth charts: the standard in Brazil — measure how the baby should grow, not just how they grow
→A single percentile does not tell the whole story: what matters most is the trend over time
→Newborn weight loss is normal: up to 7-10% in the first days
→Babies triple their birth weight by age 1
→Regular pediatric checkups are essential to track the curve and detect deviations early
What Is a Growth Chart?
A growth chart is a graph that compares your baby's weight (and length/height) with thousands of other children of the same age and sex. In Brazil, we follow the World Health Organization (WHO) charts, adopted by the Ministry of Health and the Brazilian Society of Pediatrics (SBP). The child health booklet (caderneta de saude da crianca) already includes these charts.
WHO Chart (Used in Brazil)
- Built with babies from 6 countries, including Brazil
- Based on exclusively breastfed babies
- Represents how a child should grow
- Adopted by the Ministry of Health and the SBP
- International reference since 2006
CDC Chart (Used in the USA)
- Built with American children
- Includes formula-fed babies
- Represents how children grow in the US
- Used in the United States for children over 2 years
- May overestimate normal weight
Why does Brazil use the WHO chart, not the CDC?
The WHO chart was built with babies who received exclusive breastfeeding until 6 months and adequate complementary feeding — meaning it reflects ideal growth. Breastfed babies tend to gain weight faster in the first 3 months and slow down afterward, which is perfectly normal on the WHO chart. If your baby's US pediatrician used CDC charts, do not be alarmed if the percentiles differ slightly here.
Average Weight Table by Age (0 to 12 Months)
The table below shows WHO reference values at the 50th percentile (median) for weight, for boys and girls. Remember: these are average values — your baby may be above or below and be perfectly healthy.
| Age | Boys (p50) | Girls (p50) |
|---|---|---|
| Birth | 3.3 kg (7.3 lb) | 3.2 kg (7.1 lb) |
| 1 month | 4.5 kg (9.9 lb) | 4.2 kg (9.3 lb) |
| 2 months | 5.6 kg (12.3 lb) | 5.1 kg (11.2 lb) |
| 3 months | 6.4 kg (14.1 lb) | 5.8 kg (12.8 lb) |
| 4 months | 7.0 kg (15.4 lb) | 6.4 kg (14.1 lb) |
| 5 months | 7.5 kg (16.5 lb) | 6.9 kg (15.2 lb) |
| 6 months | 7.9 kg (17.4 lb) | 7.3 kg (16.1 lb) |
| 7 months | 8.3 kg (18.3 lb) | 7.6 kg (16.8 lb) |
| 8 months | 8.6 kg (19.0 lb) | 7.9 kg (17.4 lb) |
| 9 months | 8.9 kg (19.6 lb) | 8.2 kg (18.1 lb) |
| 10 months | 9.2 kg (20.3 lb) | 8.5 kg (18.7 lb) |
| 11 months | 9.4 kg (20.7 lb) | 8.7 kg (19.2 lb) |
| 12 months | 9.6 kg (21.2 lb) | 8.9 kg (19.6 lb) |
Source: WHO Child Growth Standards, 2006 — 50th percentile (median) weight by age.
Percentiles: What They Mean in Practice
Percentiles are the lines on the health booklet graph that indicate your baby's position compared to other children. During a well-child visit, the pediatrician marks the baby's weight on the graph and observes the trajectory over time.
| Percentile | Meaning | Interpretation |
|---|---|---|
| p97 | Weighs more than 97% of children | Investigate possible excess weight |
| p85 | Weighs more than 85% of children | Risk of overweight — monitor the trend |
| p50 | Median — average weight for the age | Central reference, not "the ideal" |
| p15 | Weighs more than 15% of children | Normal if stable — track the trend |
| p3 | Weighs more than only 3% of children | Investigate cause — may be normal variation or a warning sign |
A single percentile is not a diagnosis
A baby at the 15th percentile who has always been in that range may be perfectly healthy. But a baby who was at the 85th percentile and dropped to the 15th within a few months needs evaluation. What matters is the trend of the curve, not a single number.
Expected Weight Gain by Quarter
Weight gain is not constant — it naturally decelerates throughout the first year. It is common for parents to worry when the baby gains less weight in the second half, but this is physiological, especially in babies who start moving more and begin solid foods.
| Period | Average Gain/Month | Total Gain in Quarter | Note |
|---|---|---|---|
| 1st quarter (0-3 months) | 700 to 1,000 g | ~2.5 kg | Fastest growth phase |
| 2nd quarter (3-6 months) | 500 to 600 g | ~1.7 kg | Natural deceleration — expected |
| 3rd quarter (6-9 months) | 300 to 400 g | ~1.0 kg | Baby more active and starting solids |
| 4th quarter (9-12 months) | 200 to 300 g | ~0.8 kg | Crawling/walking — higher energy expenditure |
Source: Brazilian Society of Pediatrics — Nutrition Department Guidance Manual, 2024.
Worried about your baby's weight gain?
Dr. Paula evaluates the growth chart calmly and provides guidance on nutrition and development.
Talk to the PediatricianLow Weight: Causes and When to Worry
Poor weight gain (also called "failure to thrive") occurs when the baby does not gain weight as expected or drops two or more percentile lines on the growth chart. The causes can be simple or complex.
Most Common Causes of Poor Weight Gain
Feeding-Related
- Difficulty with breastfeeding (poor latch, low supply)
- Insufficient milk or formula intake
- Late or inadequate food introduction
- Significant picky eating
- Incorrect formula dilution
Medical Conditions
- Severe gastroesophageal reflux
- Food allergy (CMPA, for example)
- Recurrent urinary tract infections
- Lactose intolerance or celiac disease
- Congenital heart defects
- Prematurity (curve adjusted for gestational age)
Warning Signs for Low Weight
See the pediatrician if the baby shows:
- !Drop of 2 or more percentile lines on the growth chart
- !Weight below the 3rd percentile without justification (such as prematurity or small parents)
- !Baby always sleepy, without energy to feed
- !Fewer than 4-6 wet diapers per day (signs of dehydration)
- !Loss of developmental milestones or significant delay
High Weight: When It Is Excessive
In the first 6 months, excess weight is rare in exclusively breastfed babies — breast milk has natural self-regulation mechanisms. However, some points deserve attention:
Breastfed baby at the 97th percentile: in the vast majority of cases, it is constitution — not obesity. Breastfed babies self-regulate and generally adjust their weight when they start crawling and walking.
Formula-fed baby well above the p97: check whether dilution is correct, whether excessive volume is being offered, or whether the formula is appropriate for the age.
After 6 months with persistent rapid gain: assess whether complementary feeding is balanced — avoid excess simple carbohydrates, juices, and ultra-processed foods.
Childhood obesity starts early
Studies show that excessive weight gain in the first year of life is associated with higher risk of obesity in childhood and adulthood. That is why it is never too early to adopt healthy eating habits — and the best prevention starts with breastfeeding and food introduction without sugar, salt, and ultra-processed foods.
Newborn Weight Loss: When It Is Normal
Every newborn loses weight in the first days of life — and this alarms many parents, especially first-time ones. Understanding this process helps you stay calm.
7-10%
Maximum normal loss
of birth weight
3-5 days
Peak loss
when weight is lowest
10-14 days
Full recovery
back to birth weight
When newborn weight loss is NOT normal
- Loss greater than 10% of birth weight
- Baby has not regained birth weight by 14 days of life
- Baby has fewer than 3 wet diapers per day by day 5
- Severe jaundice associated with excessive sleepiness
- Persistent difficulty latching — seek help with breastfeeding
How to Monitor Baby's Weight at Home
While professional monitoring at well-child visits is irreplaceable, there are ways to track growth at home without generating unnecessary anxiety.
Use a digital baby scale: weigh at the same time, without clothes, and before feeding. Once a week is sufficient in the first months.
Record in the health booklet: plot the weight on the curve to visualize the trend. Bring the booklet to every appointment. International families: ask your pediatrician for the WHO chart if your booklet uses CDC.
Observe indirect signs of good nutrition: 6 or more wet diapers per day, active and alert baby, hydrated skin, adequate length gain.
Do not compare with other babies: each child has their own genetic potential. Children of smaller parents tend to be smaller — and that is perfectly normal.
Avoid daily weighing: daily variations of 50-100 g are normal (hydration, feeding, diaper) and generate unnecessary anxiety. Weigh weekly or at each appointment.
Want to have your baby's growth chart evaluated?
During the well-child visit, Dr. Paula analyzes growth, nutritional guidance, and developmental milestones — all with time and attention.
Talk to the PediatricianWhen to See the Pediatrician
In addition to routine checkups, seek pediatric evaluation if you notice any of these signs:
- !The baby has not gained weight for 2 consecutive weeks (except in the first days of life)
- !Drop of 2 or more percentile lines on the curve
- !The baby repeatedly refuses feeding (breast or solids)
- !Frequent vomiting or persistent diarrhea
- !The baby is lethargic, excessively sleepy, or irritable without apparent cause
- !You were advised to supplement with formula but weight remains stagnant
- !Weight gain is very rapid (climbing percentiles quickly) without clear explanation
Scientific References
- WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards: Length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age. Geneva: WHO, 2006.
- Sociedade Brasileira de Pediatria. Manual de Orientacao — Departamento de Nutrologia. 4th edition, 2024.
- Ministerio da Saude. Caderneta de Saude da Crianca — WHO Growth Charts. Brasilia, 2025.
- de Onis M, Garza C, Onyango AW, Borghi E. Comparison of the WHO child growth standards and the CDC 2000 growth charts. J Nutr. 2007;137(1):144-148.
Last updated: March 20, 2026
Want to learn more about your baby's development? Read our guide on developmental milestones month by month, about breastfeeding in the first days, and about baby sleep — topics that go hand in hand with healthy weight gain. Also check our articles on baby colic and how to choose a pediatrician in Sao Paulo.
Worried About Your Baby's Weight?
Schedule a consultation for growth assessment and nutritional guidance.
Consultório no Itaim Bibi, São Paulo | CRM-SP 204778 | RQE 131771
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