Effect of birth weight and weight change during the first 96 hours of life on childhood body composition - path analysis

Abstract

Background: It is established that growth during early life is predictive of several health outcomes later in life, including body composition. The role of fetal vs postnatal growth remains controversial. We aimed to evaluate the effect of birth weight (BW) and newborn weight change (NWC) during the first 96 h of life on body composition during childhood, measured by: body mass (BMI), fat mass (FMI), and fat-free mass indexes (FFMI), waist circumference (WC) and waist-to-height ratio (WHtR). Methods: As part of the Generation XXI birth cohort, children were recruited in 2005/2006 at all public units providing obstetrical and neonatal care in Porto, Portugal. Information was collected by face-to-face interview and abstracted from clinical records. Newborn’s anthropometrics were obtained by trained examiners and NWC was estimated as (weight−BW)/BW × 100, adjusted for age in hours. At age 4 and 7, children were re-evaluated and anthropometric measurements were taken according to standard procedures. Life course data for 717 full-term singletons were presented. Path analysis was used to compute adjusted regression coefficients (β) and 95% confidence intervals. Results: BW had a direct effect on body composition at age 4: for each 100 g increase in BW, there was an increase of 0.043 (0.024; 0.062) on BMI, 0.037 (0.020; 0.055) on FMI, 0.024 (0.007; 0.042) on FFMI, 0.048 (0.031; 0.066) on WC, and 0.022 (0.004; 0.039) on WHtR z-scores. At age 7, BW was positively associated with body composition measures, but this effect was mediated by body composition at age 4. NWC had no effect on body composition at ages 4 or 7. Positive associations were found between body composition at ages 4 and 7. Conclusion: It appears that childhood body composition is programmed by fetal growth and this intra-uterine period seems more important to the development of body composition than immediate postnatal period.