Morphology of sections through the fetal heart

Two human embryos, of 28 and 29 mm crown-rump length, were studied. One had been serially sectioned in the transverse plane, the other in the sagittal plane. With the help of a graphic reconstruction method two new sets of sectioning planes were constructed. One set started from the transverse plane, which was gradually angulated towards the frontal plane. The other set started from the sagittal plane, which, too, was angulated towards the frontal plane. These procedures were carried out at various levels in both cases. We produced a continuous series of sectioning planes of the young fetal heart, which together give a clear representation of spatial morphology. We believe that these images can be of help in the interpretation of fetal echocardiograms. The morphology of these young fetuses differs considerably from older stages in that the atrioventricular septum is not yet present. Full development of the tricuspid valve and the mitral valve can only later lead to the different septal attachments of the two valves.