Final answer:
The nurse's priority when preparing for a home birth is to ensure there is safe, rapid, and available transportation to a hospital in case of emergencies during childbirth.
Step-by-step explanation:
When a nurse is helping a pregnant woman prepare for a planned home birth, the action that takes priority is ensuring the woman has safe, rapid, and available transportation to a nearby hospital. It is crucial because, during childbirth, complications can develop quickly and access to a medical facility is vital for the safety of both the mother and the baby. This priority action aligns with the knowledge that the physiology of labor is a complex process with three stages, requiring immediate medical support if complications arise. While advising the woman to get a prescription for pain medication filled beforehand is helpful, and providing a list of local obstetricians who may assist at a home birth is informative, none is as critical as ensuring a rapid transition to a hospital if necessary. Attempting to convince the woman that giving birth at the hospital is a better choice is not a priority action and should be avoided as it may go against the woman's personal choice and preparation for a home birth.