The fetal circulatory system is unique and undergoes significant changes after birth. In utero, the fetus receives oxygenated blood through the placenta and umbilical cord. The circulatory system includes structures like the foramen ovale and ductus arteriosus, which help bypass the lungs since the fetus does not breathe air. After birth, these structures close, and the circulatory system adapts to life outside the womb.