Z‐scores for fetal left atrial size and left atrium–descending aorta distance in fetuses with isolated total anomalous pulmonary venous connection

OBJECTIVES: To construct Z-score reference ranges for fetal left atrial (LA) size and left atrium-descending aorta distance (LDD or 'post-LA distance') at 20 to 40 weeks' gestation and to compare these parameters between fetuses with isolated total anomalous pulmonary venous connection (TAPVC) and normal fetuses. METHODS: Three hundred thirty-three normal singleton fetuses from 20 to 40 weeks' gestation were enrolled in a prospective cross-sectional study. Six cardiovascular dimensions were obtained by two-dimensional echocardiography. Z-score reference ranges of these measurements were determined against gestational age (GA) and fetal biometric variables, using regression analysis of the mean and standard deviation. Also, we reviewed fetal echocardiograms from ten fetuses with postnatal diagnosis of isolated TAPVC and made the measurements on archived images. Subsequently, all parameters were compared between the normal and TAPVC groups. RESULTS: A simple linear regression model was the best description of the mean and standard deviation of most variables in normal cases, with the exception of the mean LDD based on GA, which was best fitted by a quadratic regression. Fetuses with TAPVC had significantly lower LA size Z-scores [80% (8/10) of which were under -2] and increased LDD Z-scores [100% (10/10) of which were greater than 2]. Using an LDD Z-score of >2.22 was both highly sensitive (100%) and specific (98.5%) for distinguishing between TAPVC and normal hearts. CONCLUSION: Normal data and Z-scores of fetal LA size and LDD were provided against GA and fetal biometry. This could be useful for quantitative assessment of fetal TAPVC. Increased post-LA distance and decreased LA size may be markers for the prenatal diagnosis of TAPVC.