Final answer:
The highest priority test in this case is the Stat CBC in labor and delivery.
Step-by-step explanation:
The test with the highest priority in this situation would be the Stat CBC in labor and delivery. Labor and delivery is a critical and time-sensitive situation, as the health and well-being of both the mother and baby are at stake. The Stat CBC would provide important information about the mother's blood count and help identify any potential complications. In emergencies like this, ensuring the immediate safety and well-being of the patient takes precedence.