Newborn being held upside down to help drain fluid from its lungs. Inside the uterus, the foetus is suspended in amniotic fluid, which acts to cushion it from injury. This fluid lines the airways of the lungs, as they are not required for gas exchange at this point. However, the newborn's lungs will be required to take over the umbilical cord's task of exchanging oxygen and carbon dioxide, so the fluid must be replaced by air. This can be done through absorption of the fluid by pulmonary blood and lymph vessels, but holding the newborn upside down so the fluid can partially escape via the mouth can greatly assists this task.