Gestational age, intrauterine growth and body composition at 11 years of age

To assess the association of gestational age (GA) and intrauterine growth with body composition at 11 years of age.

Analysis of data from the 2004 Pelotas birth cohort, whose outcomes were fat mass (FM, kg), fat mass index (FMI, kg/m2), fat-free mass (FFM, kg), fat-free mass index (FFMI, kg/m2) - measured by air displacement plethysmography - and body mass index for age (BMI/age, Z-score). The exposures of interest were the gestational index (GA) of infants born at less than 33 weeks, from 34 to 36 and from 37 to 41, and intrauterine growth categorized as small (SGA), adequate (AGA) and large (LGA) for gestational age. Analysis of variance was used to compare means and linear regression was used to assess the strength of association. The analyses were adjusted according to variables collected at birth, such as monthly family income, maternal characteristics - education, age, pre-gestational body mass index (BMI), weight gain during pregnancy, smoking during pregnancy, type of delivery, and parity - and adolescent characteristics - skin color and birth weight. For analysis, FM and FMI underwent logarithmic transformation due to data asymmetry.

A total of 3,401 adolescents were analyzed, including boys and girls born at less than 33 weeks, with lower FM and FFM means than those born at term. However, in the adjusted analyses, there was no association between GA and any of the outcomes in either sex. LGA boys had a 10.5% higher FMI (p = 0.026) and +0.3 BMI/age Z-score (p = 0.019) as compared to AGA boys, and LGA girls had +0.3 kg/m 2 of FFMI (p = 0.039) than AGA girls.

GA was not associated with body composition at 11 years of age. However, LGA boys had higher BMI and BMI/age Z-score, and LGA girls had higher FFMI than AGA girls.