Final answer:
The nurse should be most concerned about the presence of subinvolution if a persistent, enlarged uterus occurs. Subinvolution refers to the delayed return of the uterus to its pre-pregnancy size.
Step-by-step explanation:
The nurse should be most concerned about the presence of subinvolution if persistent, enlarged uterus occurs. Subinvolution refers to the delayed return of the uterus to its pre-pregnancy size. In this case, if the uterus remains enlarged instead of gradually shrinking, it could indicate an underlying issue such as retained placental fragments, infection, or uterine atony.