INTRODUCTIONThis study aimed to determine the early growth patterns of preterm infants who required prolonged hospitalisation in terms of body weight Z-score, and to explore the influencing factors and predictors of their growth.

METHODSThe criteria of enrolment included preterm birth, singleton pregnancy, hospitalisation within the first 24 hours of life, hospital stay ≥ 28 days and clinical follow-up beyond 91 days of corrected age. Body weight Z-scores and the incidence of underweight infants were reviewed periodically, and the influencing factors and possible predictors of growth analysed.

RESULTSBody weight Z-scores of all infants of gestational age (GA) groups kept decreasing, with a trough seen at 36 weeks corrected gestational age (CGA). At corrected full-term, body weight Z-scores for all birth weight groups achieved birth level and were higher than that at 36 weeks CGA. Body weight Z-scores at 61 days corrected age was (-0.300 × GA [weeks] + 0.210 × birth weight [g] + 0.682 × body weight Z-score) at 40 weeks CGA. The cut-off values for body weight Z-score at birth (cut-off, -1.79; sensitivity, 100%; specificity, 91.3%) and 61 days corrected age (cut-off, -1.95; sensitivity, 100%; specificity, 97.1%) were selected to predict the risk of being underweight at 183 days corrected age.

CONCLUSIONEarly growth restriction is a practical problem in preterm infants with prolonged hospitalisation. Body weight Z-scores at 40 weeks CGA and 61 days corrected age can be used to predict body weight gain prior to 183 days corrected age in these infants.