Normal anatomy of fetal heart- color Doppler ultrasound:

This color Doppler ultrasound video clip of the normal fetal heart, shows the flow across the foramen ovale, from the right atrium to the left atrium (seen in red). RA= right atrium, LA= left atrium, LV= left ventricle, RV= right ventricle. This was a normal 3rd trimester fetus.                                                                  

This B-mode ultrasound video clip shows the fetal heart in a 4 chamber view, with the the foramen ovale in the interatrial septum. Note the valve of the foramen ovale bulging into the left atrium as blood gushes from the fetal right atrium to left atrium. As pressure builds in the left atrium, after birth, the valve leaflet of the foramen ovale presses against the foramen, and closes this opening.
Another video clip of the normal mobility of the fetal foramen ovale valve (see below). The arrow heads point to the foramen ovale valve.

                                                                                      

For more images and material on normal fetal heart, and cardiac anomalies visit:

http://www.ultrasound-images.com/fetal-heart.htm