A Novel Method to Describe Early Offspring Body Mass Index (BMI) Trajectories and to Study Its Determinants

Abstract

Background: Accurately characterizing children's body mass index (BMI) trajectories and studying their determinants is a statistical challenge. There is a need to identify early public health measures for obesity prevention. We describe a method that allows studies of the determinants of height, weight and BMI growth up to five years of age. We illustrated this method using maternal smoking during pregnancy as one of the early-life factors that is potentially involved in prenatal programming of obesity.

Methods: Individual height and weight trajectories were fitted using the Jenss-Bayley model on 28,381 and 30,515 measurements, respectively, from 1,666 children to deduce BMI trajectories. We assessed global associations between smoking and growth trajectories and cross-sectional associations at specific ages.

Results: Children exposed in late pregnancy had a 0.24 kg/m2 (95% confidence interval: 0.07, 0.41) higher BMI at 5 years of age compared with non-exposed children. Although the BMIs of children exposed during late pregnancy became significantly higher compared with those of non-exposed children from 2 years onwards, the trajectories began to diverge during the first weeks of life.

Conclusion: Our method is relevant for studies on the relationships between individual-level exposures and the dynamics and shapes of BMI growth during childhood, including key features such as instantaneous growth velocities and the age or BMI value at the BMI infancy peak that benefit from the monotonic pattern of height and weight growth.

Fig 1. Levels of the “One-step” and “Two-step” Modeling Methods of Growth for Children from the EDEN study aged from birth to 5 years.

Fig 2. Weight Growth Trajectories from birth to 5 years by deciles of weight growth parameters (Ai, Bi, Ci and Di) in Children of the EDEN Study, France, 2003–2012.

Fig 3

A1) Weight (kg), B1) Height (cm), and C1) BMI (kg/m²): Mean Trajectories in each category of Maternal Smoking for children from the EDEN Study aged from birth to 5 years. A2) Weight (kg), B2) Height (cm), and C2) BMI (kg/m²): Differences in Trajectories between each category of Maternal Smoking and the Reference Category (No Smoking) for children from the EDEN Study aged from birth to 5 years. Mean Trajectories are illustrated for Boys breastfed less than 3 months with 30 year-old non-overweight mothers with a high-school education or less born in Poitiers.