Superior vena cava diameters in normal Thai fetuses.

ABSTRACT

OBJECTIVE: Establish the normative data of fetal superior vena cava (SVC) diameters from 20 to 38 weeks' gestation in Thai fetuses. MATERIAL AND METHOD: Thai pregnant women with normal fetuses were enrolled for 2-dimensional echocardiographic measurements of SVC diameters. All women had good menstrual history and a confirmed gestational age with first or second trimester ultrasound. The SVC diameters were obtained in caval long-axis view in both systolic and diastolic periods. The measurements were plotted against gestational age. The best-fit regression equations were obtained. The 5th, 50th, and 95th percentile were then calculated for each gestational age. RESULTS: Three hundred three measurements were obtained. Regression analysis demonstrated a linear correlation between SVC diameter and gestational age in both early ventricular systolic and end ventricular diastolic periods. The best-fit equations were SVC maximum diameter (mm) = -1.379 + 0.183GA (week), r = 0.889 (p < 0.001), SVC minimum diameter (mm) = -1.194 + 0.134GA (week), r = 0.826 (p < 0.001) at early systolic and end diastolic periods respectively. The calculated values of the SVC diameters across gestational age were presented as 5th, 50th, and 95th percentile. CONCLUSION: SVC diameter increases linearly across gestational age in both ventricular systolic and diastolic periods. These could be a basis for assessment of fetuses with abnormal cardiovascular physiology such as hydrops fetalis and intrauterine growth restriction.