Final answer:
An oral temperature of 100.8° F (38.2° C) should be reported immediately after childbirth as it could indicate a postpartum infection, while the other assessments are normal.
Step-by-step explanation:
Among the given options, a nurse should report an oral temperature of 100.8° F (38.2° C) to the primary care provider immediately. This could be indicative of postpartum infection, such as endometritis, which is a potential complication following vaginal delivery. The respiratory rate of 16 breaths per minute and a pulse rate of 75 beats per minute are within normal limits, and a uterine fundus 1 cm below the umbilicus is a normal finding 24 hours postpartum as the uterus contracts and returns to its pre-pregnancy size.