Birth ponderal index and body mass index reference curves in a large population

Area of Science:

• Neonatal anthropometry
• Pediatric growth assessment

Background:

• Assessing neonatal weight requires accurate indices that account for gestational age and gender.
• Traditional indices like Rohrer's and Quetelet's have different applications in evaluating infant growth.
• Understanding the optimal index for neonatal assessment is crucial for clinical practice.

Purpose of the Study:

• To determine the optimal exponent for a Weight/Length index to assess neonatal weight.
• To evaluate Rohrer's index (Weight/Length^3) and Quetelet's index (Weight/Length^2) for neonatal anthropometry.
• To generate gestational age- and gender-specific percentile curves for these indices.

Main Methods:

• Analysis of a large cohort of 100,716 newborns born between 1984-1988.
• Estimation of the exponent (β) in Weight/Length^β to achieve length independence.
• Development of percentile curves for Quetelet's and Rohrer's indices from 32 to 42 weeks of gestational age.

Main Results:

• The exponent β was found to vary with gestational age but approximated 3, supporting Rohrer's index.
• Rohrer's index (Weight/Length^3) is a good approximation for overall neonatal weight assessment.
• Quetelet's index (Weight/Length^2) may be a better indicator of neonatal fat mass.
• Significant variations in index values were observed across gestational ages and between genders.

Conclusions:

• Rohrer's index provides a robust approximation for neonatal weight assessment, considering length.
• Quetelet's index is a valuable tool for assessing neonatal body composition, specifically fat mass.
• Gestational age- and gender-specific percentile curves are essential for accurate interpretation of neonatal anthropometric indices.