Which statement indicates a normal fetal circulation as observed in a fetal heart ultrasound?

The statement indicating a normal fetal circulation as observed in a fetal heart ultrasound is characterized by the presence of a right-to-left shunt between the atria. In fetal circulation, the foramen ovale, an opening between the right and left atria, allows blood to flow from the right atrium to the left atrium. This shunt is essential because it enables oxygenated blood, which is coming from the placenta via the umbilical vein, to bypass the non-functioning lungs and directly enter the systemic circulation. The right-to-left shunt is a normal and necessary aspect of fetal hemodynamics, adapting to the unique needs of the fetal environment.

Additionally, while returning blood to the placenta through the umbilical vein is a relevant aspect of fetal circulation, it doesn't specifically address the conditions observable on a fetal heart ultrasound in the same direct manner as the right-to-left shunt. The return of blood to the right atrium from the pulmonary system doesn't accurately represent the typical fetal circulatory pattern, as much of the blood bypasses the lungs. Similarly, a shunt between the umbilical arteries would not be indicative of normal fetal circulation, as these arteries carry deoxygenated blood from the fetus back to the placenta.