Cardiovascular changes at birth occur separately, but interdependently. The main changes are lung aeration with decrease of pulmonary vascular resistance and increase in blood flow for gas exchange and provision of left ventricular preload, as well as the loss of placental gas exchange and increase of systemic vascular resistance by clamping the umbilical cord. Pressure changes in the atria cause the foramen ovale to close. Due to pulmonary and systemic vascular resistance changes there is flow reversal in the ductus arteriosus, which starts to close as well.