BackgroundThe necessity of prostaglandin E1 (PGE) usage before arterial switch operation (ASO) in infants with d-transposition of the great arteries (dTGA) after balloon atrial septostomy (BAS) remains controversial. MethodsThis study is a single-centre, retrospective review of infants with dTGA who underwent ASO from January 2014 to December 2021. Parameters analysed included post-BAS oxygen saturation, time from BAS to PGE discontinuation, necessity of reinitiation, interval before PGE restart, and lowest saturation before PGE reintroduction. ResultsAmong the 35 cases of dTGA who underwent ASO, 31 (88%) required BAS, with 23 (65%) requiring PGE infusion. Of those 23 infants, 14 (60%) necessitated PGE reinitiation after discontinuation. A significant difference in post-BAS oxygen saturation was observed between the groups requiring PGE reinitiation (79.2% ± 4.7%) and those not needing reinitiation (89.0% ± 2.0%) (P < 0.001). The relative risk for the reinitiation group with BAS oxygen saturation levels ≤80% was 2.5 (95% confidence interval: 1.3-4.6). No disparity was observed in postoperative outcomes or PGE adverse effects such as fever, apnoea, bradycardia, and congestive heart failure requiring diuretic between the groups. ConclusionsGiven no significant differences in PGE adverse effects and a 2.5 times higher risk of reinitiation with post-BAS saturation below 80%, maintaining PGE until saturation reaches 80% for a few days before discontinuation may help reduce the risk of rebound hypoxaemia.