Final answer:
The first action a nurse should take if a client has a soaked perineal pad and blood underneath her buttocks post-delivery is to assess the fundus for firmness to rule out uterine atony and postpartum hemorrhage.
Step-by-step explanation:
If a nurse discovers that a client's perineal pad is soaked with blood and there is blood underneath the client's buttocks just six hours after vaginal delivery, the priority action to take is B. Assess the fundus for firmness. This assessment is crucial to detect if there is uterine atony, which can lead to postpartum hemorrhage, a potentially life-threatening condition. If the uterus is not firm, massage is indicated to stimulate contractions and stop the bleeding. This action should be performed before changing the pad or calling the healthcare provider because it could provide immediate control of the situation. If the fundus is firm but heavy bleeding continues, or if the nurse is unable to reach or maintain a firm fundus, then A. Call the healthcare provider should be the subsequent action. Changing the pad and administering pain medications are also important but are not the first actions in the event of significant bleeding.