Final answer:
Option C. When a woman in active labor experiences a drop in fetal heart rate during contractions, indicating potential fetal distress, the priority nursing action is to notify the healthcare provider immediately for further evaluation and possible intervention.
Step-by-step explanation:
The student's question pertains to the priority nursing action for a woman in active labor whose fetal heart rate (FHR) is dropping during contractions. Given that the FHR is reaching 90 beats/min for periods lasting 20 seconds during uterine contractions, this could indicate fetal distress. It is critical for the fetus to receive oxygenated blood between contractions to prevent distress.
The priority nursing action in this case, given the information provided, would be to notify the healthcare provider. This is because a sustained decrease in FHR during contractions can be a sign of significant fetal distress, warranting urgent assessment by a healthcare provider and possibly leading to emergency interventions such as the administration of oxygen to the mother, modification of maternal position, or in some cases, preparation for an emergency cesarean section. The other options, such as administering oxygen and preparing for a cesarean section, may be subsequent steps based on the healthcare provider's evaluation.