Final answer:
The nurse would be most concerned by a decrease in fetal movement during the day, as this could indicate a potential problem with the baby's well-being.
Step-by-step explanation:
The nurse would be most concerned by statement d) 'I notice a decrease in fetal movement during the day.' Decreased fetal movement could be a sign of fetal distress or a potential problem with the baby's well-being. It is important for the nurse to conduct further assessment and possibly alert the healthcare provider to ensure the safety of both the mother and the baby.