Variation of weight for age Z scores in preterm infants with extrauterine growth restriction

Objective To understand variation of weight for age Z scores in premature infants with extrauterine growth restriction(EUGR). Methods Retrospective analysis was adopted with the data of very-low-gestational age(VLGA) preterm infants who met with the following criteria: admitted to Neonatal Medical Center of Huai'an Maternity and Child Healthcare Hospital from January 2011 to December 2013, gestational age <32 weeks, more than 4 weeks of hospital stay and survived when discharged.All VLGA premature infants were divided into non-EUGR group and EUGR group according to whether the standard weight on hospital discharge was below the 10th percentile of body weight at corrected age.The weight for age Z scores of preterm infants were calculated at each time point.The differences and trends between 2 groups were compared.The receiver operating characteristic (ROC) curve in diagnosing EUGR by weight for age Z scores was drawn. Results A total of 177 VLGA premature infants were enrolled, and among them there were was 104 cases of EUGR and the incidence amounted to 58.8%.The weight for age Z scores curve of EUGR group was under that of all preterm infants, and the curve of non-EUGR group was above that of all preterm infants.The weight for age Z scores of all preterm infants and EUGR group showed overall downward trend along with prolonged hospitalization.However, the weight for age Z scores of non-EUGR group did not change significantly at each week point except for the first week.The weight for age Z scores of EUGR group was lower than that of non-EUGR group at birth (-0.84±0.39 vs -0.31±0.41), the first week after birth (-1.19±0.36 vs -0.74±0.40), the second week after birth (-1.17±0.36 vs -0.68±0.40), the third week after birth (-1.23±0.34 vs -0.64±0.39), the fourth week after birth (-1.35±0.41 vs -0.65±0.42), the fifth week after birth (-1.45±0.41 vs -0.56±0.38), the sixth week (-1.54±0.49 vs -0.70±0.36) and on discharge time (-1.72±0.38 vs -0.67±0.42). The difference at each week point was statistically significant (all P=0.000). The weight for age Z scores on discharge were negatively correlated with start time of enteral feeding in preterm infants (r=-0.271, P<0.05), time of parenteral nutrition up to 418 kJ/(kg·d)(r=-0.388, P<0.05), time of full enteral feeding (r=-0.332, P<0.05), amino cumulative dose (r=-0.298, P<0.05) and fat milk cumulative dose (r=-2.221, P<0.05). Area under the curve at each week point of the weight for age Z scores predicting the EUGR gradually increased along with prolonged hospitalization.There was a statistical significance in the weight for age Z scores value at each week point on the diagnosis of EUGR(P=0.000). There was a high sensitivity and specificity at each week point. Conclusions Dynamic monitoring weight of age Z scores of the premature infants can show the nutrition and growth trend, and may be a risk warning of the preterm infants suffering from EUGR. Key words: Extrauterine growth restriction; Weight for age Z score; Infant, premature