Foetal Persistent Left Superior Vena Cava—Not Always a Benign Finding?

OBJECTIVE: To determine the proportion of patients with a persistent left superior vena cava (PLSVC) and structurally normal heart who have associated extra cardiac anomalies and/or genetic variations and to review their clinical outcomes. METHODS: A retrospective cohort study of foetuses with a prenatal diagnosis of PLSVC and structurally normal heart seen at Saint Mary's Hospital Foetal Medicine Unit Manchester, UK between January 2017 and December 2024. Outcome of the pregnancy and for the infants up to one year follow-up data was collected from Electronic Patient Records (EPR). RESULTS: Eighty cases of foetal persistent PLSVC were detected during the study period. Six were excluded from the study because of a postnatal diagnosis of congenital heart disease. 19 out of the 74 foetuses (25%) had associated extra-cardiac structural anomalies, with 5 of these diagnosed postnatally. Seven of the 74 patients (9.5%) had genetic abnormalities. CONCLUSIONS: This study shows that PLSVC detected in foetus with an otherwise structurally normal heart is associated with an increased risk of extracardiac and genetic abnormalities. Therefore, we would recommend a detailed anatomy scan by an FMU specialist in all cases. There is a notable incidence of genetic and chromosomal abnormalities, which suggests that genetic testing is warranted in this patient population.