The fetal circulatory system is formed by the end of the second month of pregnancy and continues to exist and develop until birth. The fetal circulatory system is clearly different from that of an adult.

The cardiovascular system in the body includes the heart muscle and the blood vessel system. Every day, the heart works continuously, pumping an amount of blood equivalent to about 14,000 liters of blood carrying oxygen and nutrients to the organs in the body through three main types of blood vessels: arteries, capillaries and veins.