Final answer:
The first action for a nurse when a fetus displays category 3 fetal heart rate patterns is to immediately notify the healthcare provider due to the risk of fetal distress.
Step-by-step explanation:
If a fetus is displaying occasional category 3 fetal heart rate patterns on the monitor, which can be indicative of fetal distress, the first action for the nurse to perform would be to notify the healthcare provider immediately. This is because category 3 patterns can indicate severe hypoxia and potential fetal compromise, necessitating urgent evaluation and possible intervention. Once the healthcare provider is notified, they may recommend additional actions such as changing the client's position, administrating oxygen to the client, or preparing for an emergency delivery if required.