To explore the ultrasonic features and prognosis of fetal persistent left superior vena cava (PLSVC) combined with abnormal pulmonary artery diameter/aorta diameter (PAD/AOD) and right ventricle diameter/left ventricle diameter (RVD/LVD) ratios.

A retrospectively study was carried out on the ultrasonographic features and prognosis of fetuses from January 2016 to December 2019. Thirty-six fetuses with PLSVC combined with a narrow aorta and small left ventricle without other malformations (study group) and 83 fetuses with isolated PLSVC (control group) were included in this study. According to the gestation weeks when they were diagnosed at the first time, the fetuses were divided into four groups, namely, the study group in the second trimester (21~27⁺⁶weeks) (n=17), the study group in the third trimester (28~39⁺⁶weeks) (n=19), the control group in the second trimester (n=61), and the control group in the third trimester (n=22). At the same time, fetuses in the study group were further divided into either a labor group or an induced labor group according to the pregnancy outcome. The parameters of cardiac structure were measured, and the RVD/LVD ratio, PAD/AOD ratio, and Z-score of aorta diameter (AOD) were calculated. All the parameters in the study group were compared within groups or with those of the control group. After homogeneity of variance was verified, the data were statistically analyzed by t test and non-parametric test. Outcome of the fetuses and postnatal developmental state were followed.

Compared to the control group with isolated PLSVC, the ratios of RVD/LVD (second trimester: 1.45±0.26 vs 1.08±0.24; third trimester: 1.56±0.397 vs 1.10±0.20) and PAD/AOD (second trimester: 1.81±0.45 vs 1.31±0.32; third trimester: 1.83±0.292 vs 1.32±0.30) were significantly larger, while AOD_(z-score) (second trimester: -1.80±0.63 vs -0.36±0.11; third trimester: -1.37±0.37 vs -0.06±0.29) was smaller; the differences were statistically significant (RVD/LVD: t=3.985, P=0.004; t=4.199, P＜0.001; PAD/AOD: t=-2.858, P=0.042; t=-3.142, P=0.006; AOD_(Z-score): t=-3.362, P=0.016; t=-2.272, P=0.037). For the study group in the second trimester, the 95% confidence intervals (CIs) of the structure data were: RVD/LVD: 1.32 to 1.59; AOD _(Z-score): -2.12 to -1.47; PAD/AOD: 1.58 to 2.04. For the study group in the third trimester, RVD/LVD ranged from 1.36 to 1.77, AOD_(Z-score) ranged from -1.56 to -1.18, and PAD/AOD ranged from 1.68 to 1.98. There was no significant difference in the structure data or outcomes in the PLSVC fetuses combined with abnormal PAD/AOD and RVD/LVD ratios in the same gestational weeks (P＞0.05). Follow-up results revealed that the growth and development of all the fetuses seemed normal. In the study group, the RVD/LVD ratio returned to normal in about 37.03% (10/27) of newborns in 7 days after birth. Aorta diameter returned to normal in 88.23% (15/17) of babies in 2 years after birth.

Fetuses diagnosed with PLSVC combined with a small aorta and left ventricle without structural changes mostly have the secondary changes of isolated PLSVC. They have a favorable prognosis when the parameters of cardiac structure are within some limits.