What is the first action a nurse should take if a stable preterm newborn develops apnea for more than 20 seconds?

In the situation where a stable preterm newborn develops apnea for more than 20 seconds, the appropriate initial action is to flick the sole of the newborn's foot. This technique is a form of gentle tactile stimulation that can help to encourage the newborn to take a breath. Preterm infants are particularly prone to apnea because their central nervous system is still maturing, and they may require assistance in initiating breathing.

By providing this gentle stimulation, the nurse is attempting to prompt the newborn to respond without immediately resorting to more invasive interventions. This is crucial, as maintaining a calm approach is vital in reducing stress for the newborn. If the flicking does not resolve the apnea and the infant remains unresponsive, the nurse can then consider further assessments or interventions.

Other options, while they may be relevant in cases of apnea, are not the immediate first step. Calling for assistance or checking pulse oximetry could create delays, and suctioning the airway may be indicated if there is a clear obstruction, but it isn't typically the first response in the absence of other signs.