Benn Index at birth is associated with postnatal linear growth.

While previous research has suggested that body thinness is related to subsequent linear growth in children, it is unclear whether thinness at birth is related to linear growth in newborns and catch-up growth in small-forgestational age newborns. Drawing on data from a longitudinal growth study of 3,650 full-term Swedish babies, this study examines linear growth from birth to 6 months of age in three groups of newborns with short (< -2 SDS), appropriate (-2 to 2 SDS) and long (> 2 SDS) body length for gestational age. Among infants short at birth, the Benn Index (kg/m2.69) at birth was not related to the odds of short stature (< -2 SDS) at age 6 months (odds ratio = 1.03; p > 0.10). Nonetheless, the Benn Index was positively related to growth velocity in the first 6 months of life in the short (p = 0.060), appropriate (p < 0.05), and tall (p < 0.05) for gestational age newborns. Use of the Ponderal Index (kg/m3) would give similar results. The findings suggest that nutritional status at birth is related to linear growth velocity in newborns.