Superior Vena Cava Diameters in Normal Thai Fetuses
Dennopporn Sudjai MD*, Boonchai Uerpairojkit MD*
Affiliation : * Department of Obstetrics and Gynaecology, Faculty of Medicine, Chulalongkorn University, Bangkok
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 95thpercentile were then calculated for each
gestational age.
Results : Three hundred three measurements were obtained. Regression analysis demonstrated a linear corre-
lation 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 95thpercentile.
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.
Keywords : Fetal echocardiography, Nomogram, Superior vena cava
