The association of fetal growth rate and growth in first year of life with childhood overweight: a cohort study

There is an increasing focus on the first 1000 days from conception to two years of age as a period of importance for future weight. We aimed to describe the interaction between fetal and infant growth and their association with and ability to predict childhood overweight. We used routinely collected fetal growth data from Aarhus University Hospital and child growth data from Aarhus Municipality, 2008–2018. The outcome was overweight at age 5–9 years. The fetal growth rates at weeks 28 and 34 were extracted from individual trajectories using mixed models. We identified patterns of infant BMI Z-score growth using latent class analysis and estimated odds ratios of overweight at age 5–9 years dependent on fetal and infant growth. Predictive capabilities were assessed by comparing areas under the ROC-curves (AUCROC) of the prediction models. In 6206 children, we identified three infancy growth patterns: average, accelerated, and decelerated growth. We found 1.09 (95% CI: 1.06–1.12) greater odds of being overweight for every 10 g/week increase in fetal growth rate at week 34. Compared with average growth, accelerated infant growth was associated with 1.52 (95% CI: 1.20–1.90) greater odds of overweight. Combining fetal and infant growth, children with average fetal growth and accelerated infant growth had 1.96 (95% CI: 1.41–2.73) greater odds of overweight. Fast fetal growth with decelerated infant growth was not associated with being overweight (OR: 0.79 (95% CI: 0.63–0.98)), showing that infant growth modified the association between fetal growth and overweight. When fetal growth was added to a prediction model containing known risk factors, the AUCROC remained unchanged but infant growth improved the predictive capability (AUCROC difference: 0.04 (95% CI: 0.03–0.06)). Fetal and infant growth were independently associated with overweight, but distinct combinations of fetal and infant growth showed marked differences in risk. Infant, but not fetal, growth improved a prediction model containing known confounders.