Final answer:
The multigravida at 36 weeks with decreased fetal movement is identified as the priority by the nurse, due to the potential indication of fetal distress which requires immediate assessment and intervention.
Step-by-step explanation:
A nurse on an antepartum unit is caring for four clients and must identify which one is a priority. Among the clients mentioned, the highest priority is the multigravida at 36 weeks with decreased fetal movement. Recognizing patterns of fetal movement is key to assessing fetal health, and decreased movement may indicate fetal distress. It's crucial for such a case to be promptly assessed and managed. In other scenarios, a primigravida at 38 weeks with regular contractions is also a concern, but if the contractions are not increasing in intensity or frequency, it may not be active labor. For the multigravida at 32 weeks with back pain, it is less urgent unless the pain is indicative of labor or there are additional worrisome signs. A primigravida at 28 weeks with gestational diabetes requires monitoring and management but is not generally an immediate emergency unless associated with other complications.