Introduction
Newborn weight evolution is one of the cornerstones of child health surveillance. Contrary to what many families expect, the first important event is not weight gain but physiological weight loss. During the first days of life, particularly in exclusively breastfed infants, it is normal to lose up to approximately 7–10% of birth weight. This weight loss should then stabilise and gradually reverse, with recovery of birth weight by 10–14 days of age.
Period of rapid weight gain
Once birth weight has been regained, the period of most rapid growth begins. From birth to 3 months, typical weight gain is around 150–200 grams per week, equivalent to 20–30 grams per day. During this period, most infants double their birth weight. Between 3 and 6 months, the rate slows physiologically to approximately 100–150 grams per week, and between 6 and 12 months to around 70–90 grams per week, coinciding with increasing motor activity and the gradual introduction of complementary feeding.
Interpreting growth percentile charts
More important than the absolute percentile is the child’s growth trajectory. A healthy child generally remains close to the same percentile curve over time—whether at the 10th, 50th or 90th centile. Downward crossing of two or more percentile lines should raise suspicion of insufficient nutritional intake, intercurrent illness or feeding difficulties.
Prematurity and corrected age
In preterm infants, growth should be assessed using corrected age, and a more prolonged period of catch-up growth may occur. In term infants, the type of feeding also influences interpretation: breastfed infants tend to gain weight more rapidly during the first months and somewhat more slowly after 3–4 months, while maintaining a healthy pattern on WHO growth charts.
Clinical assessment and overall context
Finally, it is important to remember that weight monitoring does not replace clinical assessment. Feeding history, physical examination, development, the social environment and direct observation of feeding are as important as, or even more important than, the number on the scale. It is the combination of these elements that allows physiological variation to be distinguished from growth faltering and guides timely, appropriate intervention.
