Abstract 14202: Prenatal Diagnosis Influences Birth Characteristics and Subsequent Postoperative Outcomes in Transposition of Great Arteries

Background: Prenatal diagnosis of transposition of great arteries (TGA) is expected to improve postoperative outcomes after neonatal arterial switch operation (ASO); however published reports give conflicting results. We aimed to determine the association between prenatal diagnosis and postoperative outcomes after neonatal ASO. Methods: Cohort study conducted among 243 newborns with TGA (70 % prenatally diagnosed) born mainly in 3 Australian states (Victoria, South Australia and Western Australia) between 2010 and 2019. Robust multivariable modelling was used to determine the influence of prenatal diagnosis on (a) birth characteristics and (b) post-operative outcomes. Mediation analysis estimated the extent to which prenatal diagnosis mediated its effects through gestational age. Results: Gestational age and birthweight centile were lower and small-for-gestational-age (birthweight <10th centile) more common (11.8% vs 1.4%) in those diagnosed prenatally. Among births which followed labour induction or prelabour caesarean, prenatal diagnosis was associated with earlier gestational age at birth [mean (SD), 38.5(1.6) vs 39.2(1.4), P=0.01]. Among births which followed spontaneous onset of labour, prenatal diagnosis was associated with earlier gestational age at labour onset [38.2 (1.8) vs 39.2 (1.4), P = 0.01]. Prenatal diagnosis was associated with longer mechanical ventilation (incidence rate ratio: 1.74, 95% CI, 1.37 to 2.21), intensive care unit (1.70, 1.31 to 2.20) and hospital stay (1.37, 1.14 to 1.66) and also a greater need for postoperative extracorporeal membrane oxygenation. Gestational age at birth mediated up to 60% of the effect of prenatal diagnosis on postoperative outcomes. Conclusion: In this Australian study, prenatal diagnosis for TGA is associated with poorer postoperative performance after neonatal ASO and a large proportion of this effect is mediated by gestational age at birth. A higher proportion of newborns with a prenatal diagnosis were also small-for-their gestational age. Addressing factors associated with earlier gestational age at birth is likely to improve postoperative outcomes.