To assess the prognosis of isolated and associated persistent left superior vena cava (PLSVC) detected in fetal life.

All cases of PLSVC found in pregnant women between 2001 and 2018 were recorded in a local cardiac malformation registry. Only PLSVC confirmed by a fetal echocardiography specialist were included. One patient lost to follow-up before birth was excluded. The primary outcome, or unfavorable outcome, was defined as termination of pregnancy, in utero death, post-natal death and severe genetic syndromes, missed antenatally.

A total of 113 cases of isolated PLSVC and 143 cases of PLSVC with associated malformations were included; respectively 111 (98.2%) and 101 (70.6%) had a live birth. The median duration of post-natal clinical and vital status follow-up was respectively 3.8 and 5.9 years in patients without event. The outcome was favorable in 111/113 (98.2%) isolated PLSVC versus 83/143 (58%) in associated PLSVC. The 5-year post-natal overall survival was estimated at 100% (95% CI: 94.2–100%) in isolated PLSVC, 97.3% (82.3–99.9%) in PLSVC with cardiac defects alone, 87.5% (57–97.3%) in PLSVC with extracardiac defects alone, 81.0% (52.6–94.6%) in PLSVC with both cardiac and extracardiac defects, 82.0% (43.3–96.3%) in PLSVC with only non-structural defects. All genetic findings and syndromes were detected in fetuses or in infants with associated PLSVC.

This large series of PLSVC confirms the frequent association with polymalformative syndromes and shows the good short-term prognosis of isolated PLSVC after birth.