The purpose of this study was to determine the influence of first-week nutrition intake on neonatal growth in moderate preterm (MP) infants. Data on neonatal morbidity and nutrition intake on day of life 7 (DoL7) were prospectively collected from 735 MP infants (32^0/7–34^6/7 weeks gestational age (GA)). Multivariable regression was used to assess the factors associated with extrauterine growth restriction (EUGR) defined as a decrease of more than 1 standard deviation (SD) in the weight z-score during hospitalization. Mean (SD) gestational age and birth weight were 33.2 (0.8) weeks and 2005 (369) g. The mean change in the weight z-score during hospitalization was −0.64 SD. A total of 138 infants (18.8%) had EUGR. Compared to adequate growth infants, EUGR infants received 15% and 35% lower total energy and protein intake respectively (p < 0.001) at DoL7. At DoL7, each increase of 10 kcal/kg/d and 1 g/kg/d of protein was associated with reduced odds of EUGR with an odds ratio of 0.73 (95% CI, 0.66–0.82; p < 0.001) and 0.54 (0.44–0.67; p < 0.001), respectively. Insufficient energy and protein intakes on DoL7 negatively affected neonatal growth of MP infants. Nutritional support should be optimized from birth onwards to improve neonatal weight growth.

In preterm infants, early nutrient intake during the first week of life often depends on parenteral nutrition. This study aimed to evaluate the influence of standardized parenteral nutrition using three-in-one double-chamber solutions (3-in-1 STD-PN) on early neonatal growth in a cohort of moderately preterm (MP) infants. This population-based, observational cohort study included preterm infants admitted to neonatal centers in the southeast regional perinatal network in France. During the study period, 315 MP infants with gestational ages between 32^0/7 and 34^6/7 weeks who required parenteral nutrition from birth until day-of-life 3 (DoL3) were included; 178 received 3-in-1 STD-PN solution (56.5%). Multivariate regression was used to assess the factors associated with the relative body-weight difference between days 1 and 7 (RBWD DoL1-7). Infants receiving 3-in-1 STD-PN lost 36% less body weight during the first week of life, with median RBWD DoL1-7 of −2.5% vs. −3.9% in infants receiving other PN solutions (p < 0.05). They also received higher parenteral energy and protein intakes during the overall first week, with 85% (p < 0.0001) and 27% (p < 0.0001) more energy and protein on DoL 3. After adjusting for confounding factors, RBWD DoL1-7 was significantly lower in the 3-in-1 STD-NP group than in their counterparts, with beta (standard deviation) = 2.08 (0.91), p = 0.02. The use of 3-in-1 STD-PN provided better energy and protein intake and limited early weight loss in MP infants.