Final answer:
The nurse should instruct the client to notify the provider in the case of persistent leg swelling when taking combined oral contraceptives.
Step-by-step explanation:
The nurse should instruct the client to notify the provider in the case of persistent leg swelling when taking combined oral contraceptives. Leg swelling can be a sign of a serious side effect called deep vein thrombosis (DVT), which is a blood clot that forms in a deep vein, often in the leg. DVTs can be life-threatening if they move to the lungs and cause a pulmonary embolism. Therefore, the client should seek immediate medical attention if they experience persistent leg swelling.