Trajectory and correlates of growth of extremely-low-birth-weight adolescents

Abstract

Background: Catch-up growth may predispose to obesity and metabolic sequelae. We sought to examine the trajectory and correlates of growth and catch up among extremely-low-birth-weight (ELBW) (<1 kg) adolescents.

Methods: A cohort study of 148 neurologically normal ELBW children and 115 normal-birth-weight (NBW) controls born during the period 1992-1995 was conducted. Longitudinal measures of gender-specific growth of ELBW children from birth, in addition to growth and measures of obesity of ELBW and NBW children at 14 y, were evaluated.

Results: Following neonatal growth failure, ELBW children had accelerated growth, but at 8 y, they still had lower weight and height z scores than NBW children. By 14 y, ELBW boys had caught up in growth to their NBW controls, but ELBW girls remained significantly smaller. ELBW children, however, did not differ from their controls in measures of obesity. In hierarchical multiple regression analyses, only maternal BMI and weight gain during infancy and childhood predicted the ELBW children's 14-y weight z scores, BMI z scores, and abdominal circumference. Perinatal risk factors, including intrauterine growth, only predicted growth up to 20 mo.

Conclusion: Maternal BMI and rate of growth, rather than perinatal factors, predict 14-y obesity among neurologically normal ELBW adolescents.

Figure 1

Mean weight and height z scores ± SD of extremely low birth weight (ELBW) boys and girls at birth, 40 weeks (term), 8 and 20 months, and 8 and 14 years, and mean weight and height z scores ±SD of normal birth weight (NBW) boys and girls at ages 8 and 14 years. Weight measures are indicated in Panel a and height measures in Panel b. Measures of ELBW boys are indicated by dots and solid lines and measures of ELBW girls are indicated by squares and dashed lines. Measures of NBW boys are indicated by diamonds and solid lines and measures of NBW girls are indicated by triangles and dashed lines.

Figure 2

Plots of weight z scores of ELBW boys and girls at 14 years vs. maternal BMI by gender illustrating the interactive effect of gender and maternal BMI on the weight z score. Estimated regression coefficients of maternal BMI on weight z score were 0.1068 (95 CI, 0.0633 to 0.1503) for girls and 0.0202 (−0.0279 to 0.0682) for boys.