Final answer:
Further nursing action is required for the postpartum client with absent deep tendon reflexes, as it can be a sign of a serious complication that needs immediate attention.
Step-by-step explanation:
The nurse is caring for four 1-day postpartum clients. The client that would require further nursing action is the one with absent deep tendon reflexes. Mild uterine cramping and lochia rubra are expected findings within the first few days postpartum. A fundus at the level of the umbilicus is also a normal finding one day after giving birth. However, absent deep tendon reflexes can be indicative of a serious complication such as magnesium toxicity or other neuromuscular issues. This requires immediate assessment and possibly urgent medical intervention to ensure the safety of the postpartum client.