Where should the pulse oximeter probe be placed to assess a newborn's preductal oxygen saturation?

To assess a newborn's preductal oxygen saturation, the pulse oximeter probe should be placed on the right hand. This choice is correct because preductal oxygen saturation refers to the measurement taken before the blood has passed through the ductus arteriosus, which is a fetal blood vessel that connects the pulmonary artery to the aorta. The right hand is closest to this anatomical location where oxygenated blood from the right atrium mixes with systemic circulation.

Using the right hand ensures that the reading reflects the oxygen saturation levels that are indicative of how well the fetus is oxygenated prior to any mixing that occurs in the ductus arteriosus, which can happen if the blood flows to the lower limbs before being fully oxygenated. Conversely, placing the pulse oximeter on the feet (either right or left) would measure postductal oxygen saturation, which can provide different clinical information regarding oxygen transfer and possible congenital issues. Therefore, the emphasis on the right hand for preductal readings is crucial for accurate assessment in the management of newborns.