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Blood coming back from the fetus’s body also enters the right atrium, but the fetus is able to send this blue blood from the right atrium to the right ventricle (the chamber that normally pumps blood to the lungs). Most of the blood that leaves the right ventricle in the fetus bypasses the lungs through the second of the two extra fetal connections known as the ductus arteriosus. The ductus arteriosus sends the bluer blood to the organs in the lower half of the fetal body. This also allows for the bluest blood to leave the fetus through the umbilical arteries and get back to the placenta to pick up oxygen.
Since the patent foraman ovale and ductus arteriosus are normal findings in the fetus, it is impossible to predict whether or not these connections will close normally after birth in a normal fetal heart. These two bypass pathways in the fetal circulation make it possible for most fetuses to survive pregnancy even when there are complex heart problems and not be affected until after birth when these pathways begin to close.