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61 Size Matters: The Risk of Chronic Lung Disease and Significant Reti-Nopathy of Prematurity

Aims: To identify prenatal risk factors for hospital–based outcomes in very preterm infants.Methods: ANZNN prospectively audits all high-risk infants (gestation <32 completed wks or birthweight (BW) <1500g) admitted to each level III newborn intensive care unit in Australia and New Zealand. Two outcomes were selected for individual analysis; chronic lung disease (CLD-any respiratory support at 36wks post-menstrual age-PMA); significant retinopathy of prematurity (ROP-stage III or greater). As local criteria for ROP screening is most often <31wks gestation or <1250g BW, a subset of babies born at <29wks was used to prevent bias towards small for gestational age infants. Data were excluded if no eye examination was recorded (n=176, 7.7%). Univariate analysis of 23 variables was undertaken and variables not significant at P <0.05 eliminated; the remainder being entered stepwise into a multivariate logistic model and rejected when they lost significance at P <0.01.Results: The study group consisted of 5599 babies born during 1998–99 who survived to 36wks PMA. Of these, 1235 (22%) had CLD. On univariate analysis having a mother who had a previous perinatal death, antepartum haemorrhage, male sex, 1 min Apgar <4, lower gestational age, lower BW for gestation, ethnicity, pregnancy induced hypertension, and both the method and presentation of birth were associated with CLD. Pre-term pre-labour rupture of the membranes was protective. ROP exams were recorded for 2111 babies born at 22 to 28 weeks gestation; stage III or more being detected in 203 (9.6%). Significantly associated with ROP on univariate analysis were gestation, BW for gestation, 1 min Apgar <4, sex and prolonged rupture of membrane. For both models, after simultaneous adjustment, factors that remained in the multivariate model were gestation, sex and BW for gestation. A dose response was demonstrated for gestation (trend P <0.0001) and BW for gestation (trend P <0.0001), with the risk of poor outcome increasing with decreasing gestation and increasing growth restriction. Being female was protective. The models were validated on comparable groups born in 2000–2001 with all Receiver Operating Characteristic curve statistics >0.80.Conclusion: The association of CLD with reduced fetal growth is biologically plausible and may be causal, as it has been demonstrated in other populations. The relationship is less clear for ROP, where historically populations have been based on BW.