Background The relationship between brain size (measured as head circumference) and body weight in human infants is allometric. This means that the relative growth rates of the body and the brain stays in a constant relation during infancy. We are in the process of developing a preterm piglet model to study nutritional interventions on the brain. Here we present an analysis of the growth pattern during the first weeks of life.

Materials and methods Piglets (n = 146) were delivered by planned C-section at 90% and 100% gestation. All piglets were part of nutritional intervention studies in which daily body weight gain and body and brain weight upon euthanasia (d0–26) were obtained.

Results An allometric scaling model was established by linear regression using the log-transformed values of brain and body weight for piglets at 4 different ages at euthanasia: -10d (preterm at birth), 0d (term at birth), 5d and 26d for term piglets. Preterm piglets aged 4–26 days at euthanasia (n = 52) gained less weight after birth compared to term (12 vs. 26g/(kg*d), (p < 0.01), but the relation between body and brain weight did not deviate from the allometric scaling model (mean Z-score 0.014, p = 0.94).

Conclusion As in humans, the relationship between the piglet brain and body weight appears to follow allometric scaling regardless of gestational age at birth. Preterm piglets were extra-uterinely growth-restricted but the relationship between the brain and body growth did not deviate from the normal scaling relation.