Final answer:
The nurse should watch for subinvolution of the uterus as a cause of late postpartum bleeding, which is indicated by a fundal height higher than expected for the postpartum date and the continuation of lochia rubra beyond its normal duration.
Step-by-step explanation:
The nurse should be alert to subinvolution of the uterus as a cause of late postpartum bleeding. Signs to report and document include a fundal height higher than expected for the date and the persistence of lochia rubra. In normal postpartum recovery, lochia rubra (thick, dark red discharge) typically transitions to lochia serosa (a thinner, pinkish discharge) by the second to fourth postpartum day and later changes to lochia alba (a scant, creamy, or watery discharge) towards the end of the first postpartum week. An abnormally high fundal height may indicate that the uterus is not shrinking back to its pre-pregnancy size as expected, which is a key aspect of involution. Persistence of lochia rubra beyond the usual 2-3 days may suggest that normal healing is not occurring as it should, possibly due to retained placental fragments or other issues. A low blood pressure is not necessarily indicative of subinvolution but may be associated with other complications such as hemorrhage or infection. Therefore, the correct answer is option 2, signs a and d: fundal height higher than expected for the date and persistence of lochia rubra.