Physical Activity and Spatial Memory Are Minimally Affected by Moderate Growth Restriction in Preterm Piglets

Preterm birth is associated with impaired brain functions, but it is unknown whether fetal growth restriction (GR) makes these deficits worse. Using piglets as a model for preterm infants, we hypothesized that moderate GR reduces growth rate, physical activity, and spatial memory in the first weeks after preterm birth.

Preterm pigs were delivered by caesarean section and fed until 19 days (n = 830 from 55 pregnant sows) and received intensive clinical care. GR pigs were classified as animals with the lowest 5-20% percentile birth weight within each litter and were compared with litter-mate controls (21-100% percentile birth weight). Basic motor skill development, physical activity, and morbidities (e.g., necrotizing enterocolitis) were recorded within the first week. Weight of internal organs and data from a T-maze spatial memory test were noted until 19 days.

Moderate GR and control preterm pigs (birth weights 728 ± 140 and 1,019 ± 204 g, respectively) showed similar relative weights of internal organs (relative to body), except higher adrenal gland weights in GR pigs (+20-50%, p < 0.05). This was associated with a tendency to higher plasma cortisol (p < 0.05 on day 11). GR preterm pigs showed delayed ability to stand and walk (days 2-5, p < 0.01), but physical activity and proportion of correct choices in a T-maze test (70.3 vs. 71.6%) were similar.

Moderate GR has limited effect on motor function and spatial memory in the early postnatal period of preterm pigs, despite some initial delays in basic motor skills. In the postnatal period, moderately growth-restricted preterm infants may adapt well with regards to organ growth and neurodevelopment.