Abstract
Background Foetal situs abnormalities, including situs inversus totalis (SIT), right atrial isomerism (RAI) and left atrial isomerism (LAI), are associated with substantial variation in cardiac anatomy and postnatal outcomes. This study aimed to compare prenatal characteristics, associated abnormalities, perinatal outcomes, postnatal management and survival among foetuses with SIT, RAI and LAI.Methods This retrospective cohort study included 73 foetuses prenatally diagnosed with SIT (n = 12), RAI (n = 24) or LAI (n = 37) at a tertiary foetal cardiology and perinatology centre between 2021 and 2025. Prenatal cardiac and extracardiac findings, pregnancy and neonatal outcomes, postnatal surgical management pathways, and survival were evaluated. Survival was assessed using Kaplan–Meier’s analysis, and factors associated with 1-year mortality were examined using Cox proportional hazards regression.Results Cardiac phenotypes differed significantly among groups. Interrupted inferior vena cava (IVC) occurred predominantly in LAI, whereas aortic–IVC juxtaposition, double-outlet right ventricle, anomalous pulmonary venous return and unbalanced atrioventricular septal defect were more frequent in RAI. Arrhythmias occurred exclusively in LAI. Postnatal surgical management pathways differed significantly among groups (p = 0.001), with univentricular pathway most frequent in RAI. Survival distributions did not differ significantly among SIT, RAI and LAI (log-rank p = 0.193). Exploratory multivariable analysis showed an association between right ventricular outflow tract obstruction (RVOTO) and increased 1-year mortality (HR 4.79, 95% CI 1.51–15.10; p = 0.008).Conclusions Prenatally diagnosed SIT, RAI and LAI demonstrate distinct cardiac phenotypes and postnatal management requirements. Prognosis appears to depend not only on the laterality phenotype but also on specific cardiac morphology, with RVOTO emerging as an important prognostic marker. Detailed segmental foetal echocardiography may improve prenatal risk stratification, counselling and postnatal management planning.