Fetal cardiac measurements derived in the five-chamber and the short-axis view were performed in uncomplicated pregnancies between the 20th and the 40th week of gestation. Using cine loop and zoom techniques, the diameters of the aortic and pulmonary valve were measured (n = 157) and the pulmonary trunk/aorta ratio calculated. Normal ranges for both parameters were constructed and correlated with gestational age. Both diameters showed a linear increase during gestation (aorta r = 0.87, pulmonary trunk r = 0.91). The mean pulmonary trunk/aorta ratio had a constant value of 1.25 and showed no changes throughout pregnancy. In 128 fetuses the heart width was further measured and the vessel diameters were presented in correlation to the heart width.