Final answer:
The nurse should instruct the client to empty her bladder prior to applying an external transducer for fetal monitoring to ensure accurate readings.
Step-by-step explanation:
Prior to applying an external transducer for fetal monitoring, the nurse should instruct the client to empty her bladder. A full bladder can interfere with the accuracy of the fetal monitoring readings. By emptying the bladder, the transducer can be applied directly to the abdomen, ensuring a clear and accurate recording of the fetal heart rate and contractions.