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What is a normal rate of weight gain in infancy?
C M Wright1, J N Matthews, A Waterston
1Department of Child Health, University of Newcastle upon Tyne, UK.
Insights
This study introduces a "thrive index" to accurately assess child weight gain, establishing a new lower limit for normal growth. This method corrects for "regression to the mean," improving clinical and research evaluations of pediatric weight trends.
Area of Science:
- Pediatrics
- Growth Monitoring
- Child Health
Background:
- Establishing normal weight gain parameters in children is crucial for clinical and research applications.
- Observed "regression to the mean" can distort assessments of children's growth trajectories.
- Accurate growth assessment requires methods that account for natural variations in weight gain.
Purpose of the Study:
- To define a lower limit of normality for weight gain in children aged 18-30 months.
- To develop a method correcting for "regression to the mean" in pediatric weight assessment.
- To introduce the "thrive index" as a measure of child growth discrepancy.
Main Methods:
- Analysis of weight data from an annual cohort of 3418 full-term children (18-30 months).
- Development of a method using conditional standards to adjust for "regression to the mean".
- Calculation of the "thrive index" to quantify the difference between predicted and actual child growth.
Main Results:
- A significant tendency for children at growth extremes to move towards the average was observed (e.g., 26% below 3rd centile at 6 weeks remained below at 1 year).
- The "thrive index" provided a lower threshold for normality by identifying children with significantly subnormal weight gain.
- 41% of children with subnormal weight gain were not below the 3rd weight centile, highlighting limitations of centile-based assessments alone.
Conclusions:
- The "thrive index" offers a more accurate assessment of child weight gain normality than traditional methods.
- This new index is valuable for both clinical practice and research in child health and growth monitoring.
- Understanding "regression to the mean" is essential for reliable interpretation of pediatric growth data.
Abstract:
We have retrieved weights from the Child Health records of an annual cohort of 3418 full-term children, aged 18-30 months in order to define a lower limit of normality for weight gain for both clinical and research purposes. There was a strong tendency for children at the extremes of the distribution to move inwards towards the average: only 26% of those below the 3rd centile for weight at six weeks were still below it at one year. We describe a method based on conditional standards to correct for this "regression to the mean" and produce a measure of the discrepancy between a child's predicted and actual growth: the "thrive index". The value of the thrive index below which only a minority of children fell provided a lower threshold for normality. While most children below the 3rd centile for weight at 9-24 months of age also had subnormal weight gain, 41% of those with subnormal weight gain had not fallen below the 3rd centile.