Final answer:
The nurse should expect a reduced risk of respiratory distress syndrome for the client's baby when administering betamethasone 12 mg IM.
Step-by-step explanation:
The nurse should expect a reduced risk of respiratory distress syndrome for the client's baby when administering betamethasone 12 mg IM. Betamethasone is a corticosteroid that helps mature the baby's lungs and produce surfactant, a substance necessary for proper lung function. By promoting lung maturation, betamethasone can decrease the risk of respiratory distress syndrome, which is common in preterm infants.