Figure 7: Evolution of left ventricular filling from the first trimester. a) At 8 weeks there is very short duration uniphasic ventricular filling during atrial systole (A). After 10 weeks there is a progressive contribution of filling by the passive early diastolic phase (E) . Left ventricular filling at b)14 weeks and c)23 weeks. At 32 weeks flow velocities in the early and late phases of diastole (E and A,respectively) are nearly the same. These findings are thought to relate to the changing diastolic properties of the fetal myocardium which may relax more efficiently and be more compliant with age.