Introduction: Fetal cardiac growth was studied by two-dimensional echocardiography. The size of various cardiac structures were compared with gestational age. Normal values for each measurement were determined, with special attention being paid to the differences between the right and left chambers.
Patients and methods: Ninety human fetuses with a gestational ages between 17 and 39 weeks were studied. Any structural abnormality was excluded at prenatal and postnatal examination. Aortic, pulmonary artery, tricuspid and mitral valve annulus diameters were measured with classical echocardiographic views. These variables were compared between them and plotted against gestational age. The correlations were determined by Student's T-test and regression analysis using 95% confidence limits.
Results: A good correlation (r > 0,7) between all the measurements and gestational age was obtained. In absolute values, tricuspid and pulmonary artery valve diameters were significantly greater (p < 0,01) than mitral and aortic valve diameters, respectively. Nevertheless, the diastolic diameter of the left ventricle (LV) was slightly greater than the diastolic diameter of the right ventricle (RV). Separating the data of the second trimester from of those of the third, the initial dominance of LV (RV/LV ratio = 0,93) tends to disappear and a slight dominance of RV (RV/LV ratio = 1,03) was observed at term.
Conclusion: This study establishes normal values based on two-dimensional echocardiographic cardiac measurements throughout gestational stages. The data obtained will be very useful for the prenatal diagnosis and perinatal management of certain cardiopathies like the hypoplastic left heart syndrome. The relative dominance of RV in utero was also demonstrated. The different morphology of both ventricular outflow tracts and their volume changes throughout gestation, secondary to placental resistance variation, could justify the changes in the RV/LV ratio during the intrauterine period.