ABSTRACT
The four main structures which differ from adult circulation are ductus venosus, foramen ovale, ductus arteriosus and two hypogastric arteries. Ductus venosus directs oxygenated blood from the umbilical vein to the inferior vena cava. Foramen ovale is an opening between the atria of the heart which allows blood to bypass the pulmonary circulation. Ductus arteriosus diverts blood away from the pulmonary artery back into the aorta. Hypogastric arteries direct blood from the lower extremities back through the umbilical arteries to the placenta. Red blood cells are greater in number and larger than adult blood cells. The life span of these red blood cells is shorter. Fetal haemoglobin has greater oxygen-carrying capacity. Changes in temperature and compression of the chest wall during the birth stimulate the baby to take a breath.
