Do intrauterine growth restriction and overweight at primary school age increase the risk of elevated body mass index in young adults?

The route from birth size to adult body weight runs through later growth

Birth weight alone cannot describe a person’s growth trajectory. This study asked whether the relationship between restricted fetal growth and body mass index in young adulthood depended on whether a child had become overweight during primary school.

Using measurements from three life stages. Researchers followed males from the Ribeirão Preto birth cohort with records at birth, at ages eight to eleven and at eighteen, when they were assessed for military service. The analysis included 519 participants with complete measurements at all three stages.

This sequence made it possible to test an interaction: did overweight during school age have a different relationship with BMI at eighteen among those born growth-restricted? The question goes beyond whether being born small predicts a higher or lower average BMI.

Later growth changed the association. On its own, fetal growth restriction was associated with a slightly lower BMI at eighteen. Overweight at school age was strongly associated with higher BMI in young adulthood. The increase was greater among participants who combined fetal growth restriction with overweight during school age.

The apparent contradiction is informative. A group born small can remain lighter on average while a subgroup that subsequently becomes overweight has a particularly marked increase in BMI. A single measurement at birth can conceal these different trajectories.

The study supports considering prenatal and childhood growth together when investigating developmental origins of later body size. It does not show that all catch-up growth is harmful, and it did not measure adult cardiovascular events or diabetes. Its outcome was BMI at eighteen, within a male cohort, leaving the mechanisms and longer-term clinical consequences for further investigation.