children s health issues
Overview of Heart Defects
Normal Fetal Circulation
Blood flow is different in the fetus than in children and adults. all blood returning to the heart from the body (blue blood from the veins, which is low in oxygen) goes through the right atrium and then through the right ventricle to the pulmonary artery, and from there it enters the lungs. In the lungs, the blood picks up oxygen from the air sacs (alveoli) of the lungs and also releases carbon dioxide (see Exchanging Oxygen and Carbon Dioxide ). This blood, which is rich in oxygen and appears red, returns from the lungs to the left atrium and left ventricle, and from there it is pumped out of the heart to the body through a large artery called the aorta and then through smaller arteries. In the fetus,the path by which blood circulates through the heart and lungs is different. Because the fetus is inside the uterus, it is not exposed to air, and its lungs are collapsed and filled with amniotic fluid (the fluid inside the uterus during pregnancy). Because the fetus does not breathe air while in the uterus, the fetus' blood gets oxygen through the placenta. The mother's oxygen-rich blood flows through the blood vessels of the uterus. The mother's blood does not flow directly to the fetus. Only the oxygen in the mother's blood transfers to the fetal blood in the placenta, which then passes to the fetus through the umbilical blood vessels (in the umbilical cord). Before birth, much of the blood from the veins (venous blood) coming to the right side of the heart bypasses the nonfunctioning lungs and travels through two short-cuts (shunts) to get to the fetus' body. These short-cuts are The foramen ovale, a hole between the two upper chambers of the heart, the right atrium and the left atrium The ductus arteriosus, a blood vessel connecting the two great arteries leaving the heart, the pulmonary artery and the aorta In the fetus, venous blood arriving at the heart has received oxygen from the placenta. This oxygenated blood can be delivered to the body through the foramen ovale and the ductus arteriosus, largely bypassing the nonfunctioning lungs. This circulation pattern changes immediately after birth. During passage through the birth canal, fluid is squeezed out of the newborn's lungs. With the newborn's first breath, the lungs fill with air, which brings in oxygen. When the umbilical cord is cut, the placenta (and therefore the mother's circulation) is no longer connected to the newborn's circulation, and all the newborn's oxygen comes through the lungs. Thus, the foramen ovale and ductus arteriosus are no longer needed, and they usually close within the first days to weeks of life, making the newborn's circulation the same as that of an adult. Sometimes, the foramen ovale does not close (called patent foramen ovale), but a patent foramen ovale does not usually cause any health problems. Blood flow through the heart in a fetus differs from that in children and adults. In children and adults, blood picks up oxygen in the lungs. The fetus is not exposed to air. It is inside the uterus, and its lungs are collapsed and filled with amniotic fluid. Because the fetus does not breathe air, the fetus' blood gets oxygen that passes from the mother's blood vessels to the placenta. The oxygen-rich fetal blood in the placenta passes through the umbilical blood vessels (in the umbilical cord) and enters the fetal heart. Only a small amount of blood goes through the lungs. The rest of the blood bypasses the lungs by flowing through two short-cuts (shunts): The foramen ovale, a hole between the right and left atria The ductus arteriosus, a blood vessel that connects the pulmonary artery and the aorta Normally, these two short-cuts close soon after birth. 