Final answer:
The primary reason for administering Nubain to a woman in active labor is to relieve pain.
Step-by-step explanation:
The primary reason for administering Nubain to a woman in active labor is to relieve pain. Nubain is a medication that belongs to the class of drugs called opioid analgesics, and it works by binding to opioid receptors in the brain to reduce the perception of pain. By relieving pain, Nubain can help make the labor process more comfortable for the woman.