During fetal life placenta functions as organ of respiration. The gaseous exchange occurs by process of diffusion through placental barrier. Umbilical vein supplies oxygenated blood to the fetus and umbilical arteries carry deoxygenated blood to placenta. Oxygenated blood selectively flows towards head neck and brain through Foramen ovale. Venous blood flows from pulmonary artery to descending aorta through ductus arteriosus bypassing lungs which remain in a collapsed state. Ductus venosus helps to direct blood from IVC to right atrium. During fetal life there is parallel ventricular circulation with combined ventricular output. After child is born pulmonary vascular resistance decreases and pulmonary circulation occur through expanded lungs. Systemic vascular resistance increases as there is no placental circulation. Circulation occurs in series not in parallel manner. Separate ventricular output occurs (not combined). Shunts at different levels which were essential to sustain fetal life is no more required and are closed.