The aim of this study was to investigate the changes of nitrogen balance in preterm infants with extrauterine growth restriction (EUGR) during hospitalization. A total of 64 very preterm infants admitted to the Neonatal Medical Center of Huai`an Maternity and Child Healthcare Hospital were enrolled from May to October 2014. These infants had gestational ages less than 32 weeks and were within 24 hours after birth. The enrolled infants were classified into EUGR (n=18) and non EUGR (n=46) groups according to the discharge weight being below or above the 10th percentile of the expected intrauterine growth for the postmenstrual age. The urinary urea nitrogen of the infants were assayed by the Kjeldahl method and determined at 1st, 7th, 14th and 28th day after birth. Nitrogen balance at each time point was calculated and compared between the EUGR and non EUGR groups. The incidence rate of small for gestational age (SGA) infants (33.3% vs 0.0%) in the EUGR group was higher than that in non EUGR group. The difference was statistically significant (p < 0.05). The birth weight (1.37±0.20 vs 1.63±0.27) and birth weight Z-score (-1.14±0.29 vs-0.37±0.66) in the EUGR group were lower those in non EUGR group. The difference was statistically significant (all p < 0.05). At the 1st, 7th, 14th and 28th day after birth, nitrogen balance values of all infants were negative, showing an upward trend with age. At each observation time point, the nitrogen balance values in the EUGR group were lower than those in non-EUGR group. The differences on the 1st and 28th day between two groups were statistically significant (both p < 0.05), while those on the other time point were not statistically significant (both p > 0.05). All very preterm infants of study were in negative nitrogen balance while the infants of EUGR group had more seriously negative balance.

Keywords: extrauterine growth restriction, infant, nitrogen balance, very preterm