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

A file of 100,716 children born between 1984 and 1988 in 22 maternity wards was used to estimate for each week of gestational age and gender, the exponent β which makes an index Weight/Lengthβ independent from length. It varied with gestational age but remained near 3. Therefore, Rohrer's index (Weight/Length3 ) appears as a good approximation to assess neonatal weight as a whole, taking length into account. However, literature suggests that Quetelet's index (Weight/Length2 ) might be a better indicator of fat mass. In both cases, percentile curves take gestational age into account. Curves by gestational age between 32 and 42 weeks of amenorrhea and by gender, for Quetelet's and Rohrer's indices have been plotted. The values vary with gestational age. For example, the tenth percentile of Quetelet's index shifts from 7.8-12.3 kg/m2 in boys and from 7.9-12.2 kg/m2 in girls. Am. J. Hum. Biol. 10:327-340, 1998. © 1998 Wiley-Liss, Inc.